Direct type fuel cell power generator

ABSTRACT

A direct type fuel cell power generator comprises an anode electrode including an anode catalyst layer, a cathode electrode including a cathode catalyst layer, a fuel container comprising at least two electromotive portion units, each of which comprises an electrolyte film disposed between the anode electrode and the cathode electrode, the fuel container housing a fuel therein, and a fuel flow path to supply a fuel in the electromotive portion unit. In the power generator, the fuel flow path has a flow path which produces flow-back again from the fuel container to the first electromotive portion unit via the first electromotive portion unit and the second electromotive portion unit, and which is not branched during the flow-back.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2002-346213, filed Nov. 28,2002; and No. 2003-096694, filed Mar. 31, 2003, the entire contents ofboth of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a direct type fuel cell power generatorusing methanol or a methanol aqueous solution, etc. as a fuel, and moreparticularly, to a direct type fuel cell power generator in which astable output can be obtained by improving a shape of a flow path of aflow path plate through which a fuel flows.

2. Description of the Related Art

A fuel cell is provided as a device which converts chemical energyhaving a fuel such as hydrogen, hydrocarbon, or alcohol byelectrochemical reaction. This device is expected as a power generatorof high efficiency and low pollution type.

In such fuel cells, a solid polymer type fuel cell for which an ionexchange resin film is used as an electrolyte is provided as a fuel cellwhose development has been accelerated as a power source for electricautomobile or a power supply for housing in recent years. The solidpolymer type fuel cell supplies a fuel gas containing hydrogen to ananode electrode side and an oxygen gas or air to a cathode electrodeside. In the anode electrode and cathode electrode, reactions shown in(Formula I) and (Formula II) respectively occur, and an electromotiveforce is generated.Anode electrode: 2H₂→4H⁺+4e ⁻  (Formula I)Cathode electrode: O₂+4H⁺+4e ⁻→2H₂O  (Formula II)

That is, by means of a catalyst inside of the anode electrode, anelectron and a proton are generated from hydrogen, and the electron iscaptured by an external circuit. After the proton is conducted inside ofa proton conductive electrolyte film, when the conducted proton reachesthe cathode electrode, the proton reacts on the electron and oxygen onthe catalyst inside of the cathode electrode, and then, water isgenerated. Power is generated by such an electrochemical reaction.

On the other hand, in recent years, attention has been paid to a directtype methanol fuel cell. FIG. 59 shows a structure of an electromotiveportion unit in the direct type methanol fuel cell. The direct typemethanol fuel cell is constituted by sandwiching a proton conductiveelectrolyte film 7 (for example, a perfluorocarbon sulfonic acid basedion exchange film is used, and Nafion manufactured by Du Pont Co., Ltd.or the like is preferably used) between an anode electrode 3 and acathode electrode 6. Each of the electrodes is composed of substrates 1and 5 and catalyst layers 2 and 4. The catalyst layers each areconstituted by a catalyst or a carbon black to which a catalyst has beencarried being dispersed to a perfluorocarbon sulfonic acid resin. Ingeneral, as a catalyst, there is generally used a precious metalcatalyst or an alloy of the metal. In many cases, the catalyst is usedby carrying it on a carrier such as a carbon black. As a catalyst forthe anode electrode, a Pt—Ru alloy is preferably used. Alternatively, asa catalyst for the cathode electrode, Pt is preferably used. In order todrive this fuel cell, methanol and water are supplied to the anodeelectrode side, and an oxygen gas or air is supplied to the cathodeelectrode side, whereby the reactions shown in (Formula III) and(Formula IV) occur with the anode electrode and cathode electrode,respectively.Anode electrode: CH₃OH+H₂O→CO₂+6H⁺+6e ⁻  (Formula III)Cathode electrode: (3/2) O₂+6H⁺+6e ⁻→3H₂O  (Formula IV)

That is, by means of a catalyst in the anode electrode catalyst layer,an electron, a proton, and carbon dioxide are generated from methanoland water, and the generated carbon dioxide is discharged into air. Theelectron is externally captured as a current. In addition, the protonmoves on the proton conductive electrolyte film, reaches the cathodeelectrode, and reacts on an electron and oxygen, and then, water isgenerated. Power is generated based on this electrochemical reaction.

In this direct type methanol fuel cell power generator, a closed circuitvoltage is generally 0.6 V to 0.8 V, and in actual power generation witha charge current, the voltage drops to a voltage close to 0.5 V.Therefore, in order to obtain a voltage at which operation of anelectronic circuit or electric equipment is compensated for, it isrequired to electrically connect a plurality of electromotive portionunits. Hence, there is need to stack the plurality of electromotiveportion units, and provide a flow path shape or pipe for uniformlysupplying a fuel to these units, and a variety of proposals have beenmade.

Many flow paths or pipes can be roughly divided into two structures,i.e., a parallel type flow path structure and a serial type flow pathstructure. In the parallel type flow path structure, the pipes or flowpaths guided from a fuel container housing a fuel therein are branchedby the number of electromotive portion units. In the serial type flowpath structure, one flow path circulates a plurality of electromotiveportion units sequentially.

However, in the former case, a dispersion of a fuel supply state withrespect to each electromotive portion unit, the dispersion being causedby branching of the flow paths or pipes, is prone to occur, and there isa need to make further contrivance for decreasing such a dispersion. Inthe latter case as well, since a fuel is consumed serially in aplurality of electromotive portion units, there occurs a difference inoutput due to a fuel concentration difference in electromotive portionunits positioned at the first half of the flow paths and inelectromotive portion units positioned at the latter half of the flowpaths. Also in this case, there is a need to design a fine flow pathshape for decreasing the difference.

In addition, as a method for stacking a plurality of electromotiveportion units and flow path plates, there is widely used a bipolarstructure in the anode electrodes or cathode electrodes in theelectromotive portion units are arranged in a unidirectional manner. Inthis bipolar structure, a flow path plate separating electromotiveportion units is formed of a member made of an electrically goodconductor, a fuel flow path is applied to one face of one flow pathplate to supply a fuel, an oxidizing agent flow path is applied to theother face to supply an oxidizing agent, and these flow path plates aremerely stacked alternatively in the electromotive portion units, wherebyan electrical series state can be easily obtained. That is, electricalwiring for making serial electrical outputs from a plurality ofelectromotive portion units can be eliminated, thus making it possibleto simplify a stack structure.

However, in actuality, in many cases, there is provided means in which aplurality of stack units of the number of stacks for which a mechanicalstrength or spatial restriction is compensated are disposed in parallel,each of which is electrically connected. For example, there is proposeda structure such that conductive flow path plates are insulated andaggregated with each other by using an insulating member. In ensuredownsizing of this bipolar type stack, reduction of a flow path plateitself in thickness is the most effective except an element whichdepends on an electromotive portion unit itself, and a study has beenmade from structural and material points of view.

In order to structurally reduce the thickness of a flow path plate,there are considered a method for reducing the depths of anode andcathode flow paths and a method for reducing the thickness of a layerfor partitioning the anode and cathode flow paths. In the former method,the depths of the flow paths are restricted by a pressure loss in flowpath. Theoretically, it is possible to remarkably reduce the depths ofthe flow paths as long as a burden on a pump is ignored. However, inactuality, consideration must be taken into power generation efficiencyand machining precision in an overall system including power consumed ina pump. The latter method is restricted by a fuel for a material orpermeability for an oxidizing agent, and the strength of a material isrestricted as film thickness is reduced.

Moreover, an attempt has been made to reduce a flow path plate inthickness from a material point of view. In general, as a material forflow path plate, there is often used a carbon which is a material havingelectrical conductivity. However, it is impossible to provide a purecarbon of 1 mm to 2 mm or less in thickness from the viewpoints ofstrength, permeability, and machining precision. Therefore, a slightamount of resin is permeated or mixed, whereby a material with theimproved characteristics is used. However, if a rate of a nonconductivecomponent other than carbon is increased, in general, it is difficult toprovide such a characteristic compatible with a strength of resin orplastics suitable to small molding.

Because of this, there is proposed that a metal is used as a flow pathplate in view of solving a program with strength or permeability in theabove-described carbon based flow path plate. However, the flow pathplate is provided as a portion which comes into contact with a fuel oroxidizing agent and an electrode portion and captures a current. Thus, ametal used as a material for flow path plate must have sufficientcorrosion resistance. Metals available from a chemical point of viewinclude precision metals such as gold, platinum, rhodium, iridium,ruthenium and the like. A flow path plate using these metal materialsare hardly considered to be industrially applied from a cost efficiency.Therefore, in general, in forming a metal flow path plate, there isemployed a technique for applying coating using the above precisionmetal onto an entire surface of a base material made of titanium orpartial alloy which is a base metal having slight corrosion resistance.However, also in the thus prepared flow path plate, if a scratch ofpinhole size occurs during electrode tightening, corrosion is consideredto advance from such a scratched portion. In view of the above-describedcost efficiency, currently, it is considered advantageous to use acarbon as a material for flow path plate rather than a metal.

As has been described above, a variety of attempts have been made toreduce a bipolar type stack in thickness from structural and materialpoints of view, but remarkable improvement has not been achieved. Insuch a circumstance, as one of the methods for structurally reducing thestack in thickness, in recent years, there has been proposed amono-polar type stack structure in which only an oxidizing agent or fuelis supplied to one flow path plate, and only a cathode electrode or ananode electrode is arranged on both faces of the flow path plate.

In the mono-polar structure, as compared with the bipolar structure,there is a disadvantage that an electrical series state according to aplurality of electromotive portion units cannot be easily formed merelyby stacking them because the orientations at both ends of theelectromotive portion units are not uniformed in a stacking direction.On the other hand, since only either of the oxidizing agent and fuel issupplied to one flow path plate, there is no need to make top and bottomflow paths independent of each other. Therefore, the mono-polarstructure is structurally advantageous in that the thickness ofpartitioning the top and bottom flow paths can be eliminated. Inaddition, in a flow path equivalent to a depth equal to that in thebipolar structure as well, a wet edge length is reduced, and thus, apressure loss of the flow path is expected to lower, making it possibleto further reduce the depth of the flow path.

Accordingly, a mono-polar type stack structure is expected as a stackstructure of a fuel battery power generator oriented to a portableinformation terminal, the stack structure requiring downsizing inparticular. Further, in the case where such an application isconsidered, there is expectedly proposed a mono-polar type stackstructure for direct type methanol fuel cell, in which there is a highpossibility that a direct type methanol fuel cell which does not requirea complimentary device such as a vaporizing device or refining device isused.

In the direct type methanol fuel cell, a methanol aqueous solution isconsumed at an anode electrode, and hydrocarbon that is a reactionproduct at the anode electrode is generated as air bubbles. In addition,the volume of carbon dioxide that is the generated gas is several timesas compared with a methanol aqueous solution that is a liquid to besupplied. The volume expansion of carbon dioxide in a flow path is oneof the main causes which prevents the flow of the methanol aqueoussolution in the flow path. Once prevention of the flow of the methanolaqueous solution inside of the flow path, such prevention causes a fuelsupply rate-determining at the anode electrode, and a high chargecurrent density cannot be obtained.

That is, this denotes a lowered output of a direct type methanol fuelcell, and such an output cannot be recovered until carbon dioxideretained in the flow path has been swept. This program with a gas-liquiddouble layer flow may occur in the flow path at the cathode electrodeside. However, the problem is much more serious than a problem whichoccurs inside of the flow path at the cathode electrode side by virtueof reasons such as small liquid volume change rate than gas and greaterinter-wall frictional force. That is, the above problem is more seriousin a direct type methanol fuel cell for supplying a liquid fuel than asolid polymer type fuel cell (PEM, PEFC) in which gaseous hydrogen issupplied as a fuel to the anode electrode, and further, no gaseousproduct is obtained. A flow path design from this point of view isimportant in proposing a mono-polar type flow path plate for directmethanol fuel cell.

First, in general, a cross section of a flow path is reduced in order toachieve a smooth flow of a methanol aqueous solution inside of the flowpath in the direct methanol fuel cell. This is because carbon dioxidegenerated inside the flow path is easily pushed out by efficientlyincreasing a flow rate of the fuel flowing the flow path. Further, aserpentine type flow path exhibiting a shape in which a narrow flow pathis folded back many times is well used as a flow path of a direct typemethanol fuel cell in order to deliver a fuel to an entire face of anelectromotive portion unit in a state in which the cross section of theflow path is reduced.

In particular, since this serpentine type flow path can be easily formedas a bipolar type flow path plate, in forming the bipolar type flow pathplate, the serpentine type flow path is often used. Furthermore, inorder to increase power generation efficiency, a comb type protrusionpartitioning the adjacent flow paths in an opposite manner is reduced inwidth so as to increase an area in which the electromotive portion unitand methanol aqueous solution come into contact with each other.

However, if the comb type protrusion is extremely reduced in width inorder to increase power generation efficiency, the outer-most powercollecting portion of an electrode in the electromotive portion unit isporous. Thus, air bubbles of carbon dioxide expanding therefromshort-circuits at the adjacent flow paths, and a pressure is not appliedcorrectly in a direction in which the flow path advances. Because ofthis, there occurs a problem that a fuel is retained at a flow pathportion which is short-circuited and through which no air bubbles pass.Conversely, there occurs a problem that, if a fuel short-circuit occurs,carbon dioxide is retained. Therefore, in general, the width of the combshaped protrusion structure is often designed primarily by about 1 mm.

In other words, in order to ensure proper fuel supply to the bipolartype flow path plate in the direct type methanol fuel cell, it isdesirable that a serpentine type flow path of about 1 mm in width of thecomb type protrusion structure be used. Further, it is required to pushan electrode face of the electromotive portion unit against a flow pathplate by applying a proper pressure.

However, a similar flow path structure cannot be used for a mono-polartype flow path plate. This is because, in the serpentine type flow pathproduced so as to penetrate both faces of the flow path plate, the combtype protrusion structure is established in a floated state only at onesmall portion from the periphery of the flow path plate, and even undera pressure in the flow path which is not so problematic in the bipolartype flow path plate, the short-circuit of carbon dioxide or fuel easilyoccurs. Also, a method which solves this problem is not proposed yet. Asa flow path shape of a mono-polar type flow path plate which has beenstudied in recent years, there is merely used a simple structure inwhich a plurality of linear flow paths are arranged in parallel.Accordingly, there is expectedly proposed a flow path shape forimproving power generation efficiency and a flow path plate structure ormaterial for achieving such a shape.

The above-described problems with the mono-polar structure are similarin the case of a flow path plate made of metal which can be easilyformed. As the cutting faces of the flow path plate are very large innumber, making it further difficult to increase the uniformity ofcorrosion resistance processing. In addition, as in the bipolarstructure, in the case where the electromotive portion units arearranged in parallel in a planer direction of the flow path plate, acomplicated structure via an insulating member must be unavoidablyprovided.

The following problem with the above-described direct type methanol fuelcell has occurred. That is, the direct type methanol fuel cell isexpected to be used as a power source of a portable electronic devicefrom a height of energy density of methanol which is a liquid fuel. Inaddition, there is no need for fuel pressurization from the viewpoint ofa liquid fuel. Further, there is a low possibility that a fuel leakageoccurs from a gap between a flow path and an electromotive portion unitas compared with a solid polymer type fuel cell which uses hydrogen as afuel. Therefore, unlike a fuel supply flow path of the solid polymertype fuel cell, it is considered possible to provide a comparativelycomplicated flow path structure or flow path disposition. However, thereis not proposed a flow path structure in a direct type methanol fuelcell power generator which solves problems with the parallel type flowpath and the serial type flow path, respectively.

Moreover, as long as a flow path plate consisting essentially of acarbon for power collection is used, rapid development and production ofa small sized fuel cell power generator for portable device becomesobstacle due to necessity of improvement and development of a carbonmaterial for reducing one flow path plate in thickness; necessity oftechnique for integrated molding using an insulating material for makingthe plates in parallel in a planar direction; or complication or thelike in which plural types of members are required in a productionprocess.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a directtype methanol fuel cell power generator composed of a plurality ofelectromotive portion units, the power generator being capable ofreducing a deflection in output on an electromotive portion unit by unitbasis and ensuring stable fuel supply.

In order to solve the above-described problems and to achieve theobject, a direct type fuel cell power generator according to the presentinvention is configured as follows.

According to a first aspect of the present invention, there is provideda direct type fuel cell power generator comprising: an electromotiveportion unit group composed of a plurality of electromotive portionunits formed by sandwiching an electrolyte layer between an anodeelectrode including an anode catalyst layer and a cathode electrodeincluding a cathode catalyst layer; a first flow path plate havingformed thereon a first flow path which is disposed in abutment with theanode electrode of the electromotive portion unit group and throughwhich a fuel flows; and a second flow path plate having formed thereon asecond flow path which is disposed in abutment with the cathodeelectrode of the electromotive portion unit group and through which aoxidizing agent flows, wherein the first flow path passes so as to comeinto contact with all anode electrodes in the electromotive portion unitgroup without branching from an inlet thereof to an outlet, and isformed so as to come into contact with an anode electrode of at leastone electromotive portion unit a plurality of times.

According to a second aspect of the present invention, there is provideda direct type fuel cell power generator comprising: an electromotiveportion unit group composed of a plurality of electromotive portionunits formed by sandwiching an electrolyte film between an anodeelectrode including an anode catalyst layer and a cathode electrodeincluding a cathode catalyst layer; a first flow path plate havingformed thereon a first flow path which is disposed in abutment with thecathode electrode of the electromotive-portion unit group and throughwhich an oxidizing agent flows; and a second flow path plate havingformed thereon a second flow path which is disposed in abutment with theanode electrode of the electromotive portion unit group and throughwhich a fuel flows, wherein the first flow path passes so as to comeinto contact with all cathode electrodes in the electromotive portionunit group without branching from an inlet thereof to an outlet, and isformed so as to come into contact with a cathode electrode of at leastone electromotive portion unit a plurality of times.

According to a third aspect of the present invention, there is provideda direct type fuel cell power generator comprising: an anode electrodeincluding an anode catalyst layer; a cathode electrode including acathode catalyst layer; a fuel container comprising at least twoelectromotive portion units, each of which comprises an electrolyte filmdisposed between the anode electrode and the cathode electrode, the fuelcontainer housing a fuel therein; and a flow path plate having formedthereon a flow path to supply an oxidizing agent or a fuel to theelectromotive portion unit, wherein the flow path has a flow path whichproduces flow-back again from the fuel container to the firstelectromotive portion unit via the first electromotive portion unit andthe second electromotive portion unit, and which is not branched duringthe flow-back.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective view showing a direct type methanol fuel cellpower generator according to a first embodiment of the presentinvention;

FIGS. 2A to 2D are views each showing essential portions of the directtype methanol fuel cell power generator;

FIG. 3A is a bottom view showing a flow path plate according to a firstmodified example of the flow path plate;

FIG. 3B is a bottom view showing a flow path plate according to a secondmodified example of the flow path plate;

FIG. 4 is a characteristic view showing dependency of a current voltagecharacteristic in an electromotive portion unit of a direct typemethanol fuel cell with respect to an initial concentration of amethanol aqueous solution;

FIGS. 5A to 5C are illustrative views schematically illustrating amethod for allocating a fuel flow path;

FIGS. 6A to 6C are views each showing essential portions of a directtype methanol fuel cell power generator according to a second embodimentof the present invention;

FIGS. 7A to 7D are plan views each showing a modified example of a flowpath plate;

FIG. 8 is a plan view showing a modified example of a flow path plate;

FIGS. 9A and 9B are plan views each showing a modified example of a flowpath plate;

FIGS. 10A to 10C are plan views each showing a modified example of aflow path plate;

FIG. 11 is a view showing a result of a current voltage characteristicof a direct type methanol fuel cell power generator;

FIG. 12 is a view showing a result obtained by measuring a currentvoltage characteristic under an operating condition of Example 1;

FIGS. 13A to 13C are views each showing a direct type methanol fuel cellpower generator using a serial type flow path;

FIG. 14 is a view showing a current voltage characteristic ofComparative Example 1 under the operating condition of Example 1;

FIGS. 15A to 15C are views each showing a direct type methanol fuel cellpower generator using a parallel type flow path;

FIG. 16 is a view showing a current voltage characteristic under theoperating condition of Example 1;

FIG. 17 is a view showing a result of a power generation test inComparative Example 3;

FIG. 18 is a side view showing a direct type methanol fuel cell powergenerator according to a third embodiment of the present invention;

FIG. 19A is a perspective view showing the direct type methanol fuelcell power generator;

FIG. 19B is a transverse cross section showing the direct type methanolfuel cell power generator;

FIGS. 20A to 20E are exploded views each showing the direct typemethanol fuel cell power generator;

FIG. 21 is a view showing a current voltage characteristic of the directtype methanol fuel cell power generator;

FIGS. 22A to 22C are views each showing a flow path plate having formedthereon a direct type flow path incorporated in a direct type methanolfuel cell power generator comprising four electromotive portion units;

FIG. 23 is a view showing a test result concerning a stack ofComparative Example 4;

FIG. 24 is a view showing a flow path plate having formed thereon aparallel type flow path incorporated in a direct type methanol fuel cellpower generator comprising for electromotive portion units according toComparative Example 5;

FIGS. 25A to 25E are views each showing the flow path plate havingformed thereon the parallel type flow path incorporated in the directtype methanol fuel cell power generator comprising four electromotiveportion units according to Comparative Example 5;

FIG. 26 is a view showing a result obtained by measuring a currentvoltage characteristic under an operating condition of Example 3;

FIG. 27 is a side view showing a direct type methanol fuel cell powergenerator according to a fourth embodiment of the present invention;

FIGS. 28A to 28C are plan views each showing a flow path plate of thedirect type methanol fuel cell power generator;

FIG. 29 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underthe operating condition of Example 3;

FIGS. 30A to 30C are views showing first to third flow path platesincorporated in a direct type methanol fuel cell power generatoraccording to a fifth embodiment;

FIG. 31 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underthe operating condition of Example 3;

FIG. 32A is a longitudinal cross section showing a direct type methanolfuel cell power generator according to a sixth embodiment of the presentinvention;

FIG. 32B is a sectional view showing the direct type methanol fuel cellpower generator viewed in a direction indicated by the arrow, the crosssection being taken along the line γ-γ in FIG. 32A;

FIGS. 33A to 33C are views each showing first to third flow path platesincorporated in the direct type methanol fuel cell power generator;

FIG. 34 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underthe operating condition of Example 3;

FIG. 35 is a side view showing a direct type methanol fuel cellaccording to a seventh embodiment of the present invention;

FIG. 36A is a perspective view showing the direct methanol fuel cellpower generator;

FIG. 36B is a sectional view showing the direct methanol fuel cell powergenerator;

FIGS. 37A to 37C are views showing first to third flow path platesincorporated in the direct type methanol fuel cell power generator;

FIG. 38 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underthe operating condition of Example 3;

FIGS. 39A to 39C are plan views and sectional views of essentialportions showing a direct type methanol fuel cell power generatoraccording to an eighth embodiment of the present invention;

FIG. 40 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underthe operating condition of Example 3;

FIG. 41 is a plan view and a sectional view of essential portionsshowing a flow path plate incorporated in a direct type methanol fuelcell power generator according to a ninth embodiment of the presentinvention;

FIG. 42 is a view comparatively showing a current voltage characteristicof the direct type methanol fuel cell power generator;

FIG. 43 is a plan view and a sectional view of essential portionsshowing a flow path plate incorporated in a direct type methanol fuelcell power generator according to a tenth embodiment of the presentinvention;

FIGS. 44A to 44C are views each showing a flow path plate incorporatedin a direct type methanol fuel cell power generator according to aneleventh embodiment of the present invention;

FIG. 45 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underan operating condition of Example 9;

FIG. 46 is a view showing a current voltage characteristic when thedirect type methanol fuel cell power generator has been operated underthe operating condition of Example 9;

FIG. 47 is a view showing a flow path plate incorporated in a directtype methanol fuel cell power generator according to a twelfthembodiment of the present invention;

FIG. 48A is a plan view showing a flow path plate incorporated in adirect methanol fuel cell power generator according to a thirteenthembodiment of the present invention;

FIG. 48B is a plan view and a sectional view of essential portionsshowing the flow path plate;

FIG. 49 is a flow showing a flow path plate before forming a penetratingportion;

FIGS. 50A to 50C are sectional views each showing a process for forminga penetrating portion;

FIGS. 51A to 51E are plan views each showing a modified example of aflow path plate on which a penetrating portion is provided on a boundarywall;

FIGS. 52A to 52F are plan views each showing a modified example of theflow path plate on which the penetrating portion is provided on theboundary wall;

FIGS. 53A to 53C are views each showing a flow path incorporated in adirect type methanol fuel cell power generator according to a fourteenthembodiment of the present invention;

FIG. 54A is an exploded perspective view showing a flow path platehaving formed thereon a penetrating portion incorporated in a directtype methanol fuel cell power generator according to a fifteenthembodiment of the present invention;

FIG. 54B is a perspective view showing the flow path plate;

FIG. 55 is a view showing a current voltage characteristic in the directtype methanol fuel cell power generator;

FIG. 56A is a longitudinal cross section showing a direct type methanolfuel cell power generator according to a sixteenth embodiment of thepresent invention;

FIG. 56B is a transverse cross section showing the direct type methanolfuel cell power generator;

FIGS. 57A to 57E are sectional views taken along the lines δ1-δ1 toδ5-δ5 in FIGS. 56A and 56B;

FIG. 58 is a view showing a fuel concentration by fuel concentrationbasis a relationship between a voltage and a fuel supply amount in thedirect type methanol fuel cell power generator; and

FIG. 59 is an illustrative view schematically illustrating anarrangement of general electromotive portion units.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

FIG. 1 is a schematic view showing a direct methanol fuel cell powergenerator 100 having electromotive portion units according to a firstembodiment of the present invention. FIGS. 2A to 2D are views eachshowing essential portions of the direct type methanol fuel cell powergenerator 100, in which FIG. 2A is a top view showing an insulating flowpath plate 101 positioned at the shown top side; and FIG. 2B is a bottomview showing the insulating flow path plate 101 positioned at the showntop side; FIG. 2C is a sectional view viewed in a direction indicated bythe arrow, the sectional view being taken along the line α1-α1 in FIGS.2A and 2B; and FIG. 2D is a sectional view viewed in a directionindicated by the arrow, the sectional view being taken along the lineα2-α2 in FIGS. 2A and 2B.

In FIGS. 2A to 2D, reference numeral 101 designates an insulating flowpath plate (fuel side); 102 designates an insulating flow path plate(oxidizing agent side); 103 designates a fuel flow path; 104 designatesa fuel flow path supply port; 105 designates a fuel flow path ejectionport; 106 designates a flow path cap body at a back face of the flowpath; 107 designates a resin based sealing member; 108 a and 108 b eachdesignate an electromotive portion unit; 109 denotes an air flow path;110 designates a flow path portion bent to the side of the flow path capbody 106 such that the flow path does not face the electromotive portionunits 108 a and 108 b; and 111 designates a metallic thin film forleading out a current. The electromotive portion units 108 a and 108 bemploy the above-described structure shown in FIG. 58. Referencenumerals 103 a to 103 h in FIGS. 2A to 2D designate individual regionsof the fuel flow path 103.

The fuel flow path supply port 104 of essential portions of this powergenerating portion is connected to fuel supply means via a fuel pump(not shown) so that a fuel is supplied. In addition, an air pump (notshown) for supplying an oxidizing agent such as air is connected to theair flow path 109, and an electrode terminal (not shown) is connected tothe metallic thin film 111 for leading out a current, configuring a fuelcell power generator. The shape of the air flow path 109 for supplyingan air is identical to that of a conventional parallel type flow path(refer to FIGS. 15A to 15C).

In the thus configured direct type methanol fuel cell power generator,power is generated in the following manner. That is, a fuel such as amethanol aqueous solution supplied from the fuel supply means issupplied from the fuel flow path supply port 104. Then, a fuel flowssequentially through the regions 103 a, 103 b, and 103 c of the fuelsupply flow path 103 facing the electromotive portion unit 108 a.Further, the fuel flows sequentially through the regions 103 d, 103 e,103 f, and 103 g of the fuel flow path 103 facing the electromotiveportion unit 108 b, and furthermore, the fuel is discharged from thefuel flow path ejection port 105 to the outside via the region 103 hfacing the electromotive portion unit 108 a. In this way, while the fuelflows through the regions 103 a, 103 b, 103 c, and 103 h, the fuel issupplied to an anode electrode substrate of the electromotive portionunit 108 a. While the above fuel flows through the regions 103 a, 103 e,103 f, and 103 g, the fuel is supplied to the electromotive portion unit108 b.

In the direct type fuel cell power generator according to the presentembodiment, at the fuel flow path 103 for supplying a fuel to the firstelectromotive portion unit 108 a and the second electromotive portionunit 108 b, the fuel flow path 103 passing through the secondelectromotive portion unit 108 b from the first electromotive portionunit 108 a circulates so as to supply a fuel to the first electromotiveportion unit 108 a again without branching the fuel flow path 103. Then,at a plurality of electromotive portion units 108 a and 108 b, a contactarea between the fuel flow path 103 and each of the power generatingelements of the electromotive portion units 108 a and 108 b is adjustedsuch that an amount of fuel supply is substantially equal to another,thereby making it possible to improve stability of a power generationoutput.

FIG. 3A is a bottom view showing a flow path plate 131 according to afirst modified example of the above-described flow path plate 101. InFIG. 3A, reference numeral 131 designates the flow path plate; 132designates a portion at which an electrode portion of the electromotiveportion unit 108 is disposed; 133 and 134 designate a supply port and anejection port of A fuel flow path 135; and 135 designates the fuel flowpath. In these fuel flow path shapes, a fuel is supplied to an electrodeportion of a first electromotive portion unit, and then, is supplied toan electrode portion of another electrode portion unit. Further, thefuel is then supplied to the first or another electromotive portion unitwithout branching the fuel flow path. Also in this modified example,this fuel cell power generator can achieve advantageous effect identicalto the above-described direct type methanol fuel cell power generator100.

FIG. 3B is a bottom view showing a flow path plate 141 according to asecond modified example of the above-described flow path plate 101. InFIG. 3B, reference numeral 141 designates the flow path plate; 142designates a portion at which an electrode portion of the electromotiveportion unit 108 is disposed; 143 and 144 designate a supply port and anejection port of a fuel flow path 145; and 145 designates the fuel flowpath. In these flow path shapes, a fuel is supplied to an electrodeportion of a first electromotive portion unit, and then, is supplied toan electrode portion of another electromotive portion unit. Further, thefuel is then supplied to the first or another electromotive portion unitagain without branching the fuel flow path. Also in this modifiedexample, this fuel cell power generator can achieve advantageous effectidentical to the above-described direct type methanol fuel cell powergenerator 100.

In the above first embodiment, an amount of fuel supply to theelectromotive portion unit is identical to a current density at theelectromotive portion unit, and thus, can be described as in Formula (3)in accordance with a law of conservation of weight.

$\begin{matrix}{{\frac{\mathbb{d}}{\mathbb{d}Z}\left( {\rho \cdot u} \right)} = {- \frac{50J\; S}{6F\; S_{0}L_{0}}}} & (3)\end{matrix}$

In Formula (3), Z denotes a distance (cm) from a flow path supply portof a fuel flow path; S denotes an area (cm²) of an electromotive portionunit; L₀ denotes an effective full length (cm) of a fuel flow path; S₀denotes a sectional area (cm²) of a flow path; J denotes a currentdensity (A/cm²); ρ denotes a fuel density (g/cm³) at position Z; ρ₀denotes an initial fuel density (g/cm³); “u” denotes a flow rate(cm/sec) of a fuel in a fuel flow path; and F denotes a Faraday constant96487 C/mol. A molecular weight of methanol is defined as 32, amolecular weight of water is defined as 18, and the number of electronsobtained per reaction is defined as 6. A solution of Formula (3) isobtained in accordance with Formula (4).

$\begin{matrix}{\rho = {\rho_{0} - {\frac{25J\; S}{3F\; S_{0}L_{0}} \cdot \frac{Z}{u}}}} & (4)\end{matrix}$

A fuel concentration in Formula (4) is bonded with a molar concentrationC (mol/l) of a methanol aqueous solution fuel in accordance with Formula(5) described later, and finally, Formula (6) is derived. In theformula, the density of methanol which is not diluted is defined as 0.8g/cm³.

$\begin{matrix}{\rho = {1 - \frac{C}{125}}} & (5) \\{C = {C_{0} - {\frac{3125J\; S}{3F\; S_{0}L_{0}} \cdot \frac{Z}{u}}}} & (6)\end{matrix}$

FIG. 4 is a characteristic view showing dependency of a current voltagecharacteristic in an electromotive portion unit of a direct typemethanol fuel cell with respect to an initial concentration of amethanol aqueous solution. In a measuring condition, a temperature isdefined as 70° C.; a flow rate of a methanol aqueous solution fuel isdefined as 0.07 cm/min; and a flow rate of air is defined as 11 cm/min.An electromotive portion unit whose area can be ignored in length of afuel flow path or a change of fuel concentration is used. From the fuelconcentration dependency of the current voltage characteristic shown inFIG. 4, in the case where a difference in fuel concentration is withinthe range of 10%, it is understood that a difference between voltagevalues in a charge current value at a critical charge current density of50±10% can be ignored. In accordance with Formula (6), it can beunderstood that a change in distance from a flow supply port is equal toΔC=C₀−C by a change in fuel concentration. That is, even if a flow pathlength in a given fuel concentration electromotive portion unit isdifferent from another by 10%, it is considered that a differencebetween voltage values in a charge current value at a critical chargecurrent density of 50±10% can be ignored.

In order to drive a fuel cell power generator with a fuel whose amountis as small as possible for a long period of time, it is required toimprove a rate of an amount of power generation captured by an externalcircuit in an amount of electricity having the supplied fuel, i.e., fuelutilization efficiency. However, as can be seen from Formula (6), it isevident that a decrease of the fuel concentration in the fuel flow pathis proportional to a distance from the flow path supply port, and anoutput at electromotive portion unit positioned at the latter half ofthe fuel flow path is significantly lowered as fuel utilizationefficiency from the fuel supply port to the ejection port increases.That is, this is because a significant decrease (10% or more) of thefuel concentration at the latter half of the fuel flow path leads to adecrease of the critical charge current density. Therefore, there is aneed to make contrivance for reducing a temperature difference in a fuelto be supplied to all the electromotive portion units. By using a methodfor allocating a fuel flow path described later to an electrode portion,it becomes possible to ensure that an average of fuel concentrationssupplied to the electromotive portion units is close to another amongthe electromotive portion units.

FIGS. 5A and 5B are illustrative views schematically illustrating amethod for allocating the fuel flow path defined in Formula (2). Adescription of FIG. 5C will be given later. In FIGS. 5A and 5B,reference numeral 151 designates an electromotive portion unit; 152designates a divided effective flow path region; 153 designates a flowpath region which is not effective; 154 designates a region of thedivided electromotive portion unit; 155 designates a fuel supply port ofa fuel flow path; and 156 designates a fuel ejection port of a fuel flowpath. FIG. 5A shows a correlation with a region of the divided effectivefuel flow path of b_(r,m); and FIG. 5B shows a correlation with thedivided effective flow path region of Lb_(r,m).

In FIGS. 5A and 5B, a flow path width is identical to another in anyplace; “n” denotes the number of electromotive portion units in which aflow path supplies a fuel; and “m” denotes an arbitrary electromotiveportion unit in the above electromotive portion units. “s” denotes thenumber of flows when a fuel flow path flows through electromotiveportion units, and is taken as values equal to each other in all theelectromotive portion units. That is, the fuel flow path is divided into“s” regions on an electromotive portion unit by unit basis, andentirely, is divided into “ns (≈ h)” regions. Here, in the case where afuel is supplied to the fuel flow path, all the regions of “ns”electrode portions in the figure are defined as anode electrodes. In thecase where an air flow path is provided instead of the fuel flow path,air (oxidizing agent) is supplied. In this case, all the regions of “ns”electrode portions are defined as cathode electrodes.

An arithmetic progression b_(r,m) indicates a natural number rangingfrom 1 to “h”, the number being allocated to regions divided into “h”sections, as shown in FIG. 5A. In FIG. 5A, in the fuel flow path, thefuel flows through a first region b_(1,1) a second region b_(1,2), athird region b_(1,3), . . . an “n-th” region b_(1,n). Then, the fuelflows through another region b_(2,n) in the last “n-th” electromotiveportion unit, from where the fuel flows trough regions in reversedorder, and returns to the first electromotive portion unit. In FIG. 5A,this operation is repeated s/2 times, and therefore, a lowercase letter“s” is defined as an even number.

It is indicated that an arithmetic progression b_(r,m) meet a recursionformula of Formula (7). In general, a solution of this Formula (7) canbe expressed as Formula (8), and thus, the above-described Formula (2)is derived from Formula (9) obtained by substituting Formula (7) forFormula (8).b _(r,m) −b _(r−1,m) =n+(−1)^(r−1)(2m−n−1)  (7)

$\begin{matrix}{b_{r,m} = {b_{1,m} + {\sum\limits_{i = 2}^{l}\;\left( {b_{i,m} - b_{{i - 1},m}} \right)}}} & (8) \\{b_{r,m} = {b_{1,m} + {\sum\limits_{i = 2}^{r}\;\left\lbrack {n + {\left( {- 1} \right)^{i - 1}\left( {{2m} - n + 1} \right)}} \right\rbrack}}} & (9)\end{matrix}$

As shown in Formula (6), the concentration of the fuel in the fuel flowpath decreases in proportion to a distance from the flow path supplyport. Therefore, in order to reduce a difference in fuel concentrationsupplied to the electromotive portion units each, a difference on anelectromotive portion unit by unit basis, between average distances fromthe flow path regions 1 to “s” passing through the electromotive portionunits, may be reduced. An effective length from the fuel supply port ofa flow path region “r” (1≦r≦s) divided by an arbitrary electromotiveportion unit “m” (1≦m≦n) is defined in accordance with Formula (10).

$\begin{matrix}{Z_{b_{r,m}} = {\sum\limits_{i = 1}^{b_{r,m}}\; L_{b_{r,m}}}} & (10)\end{matrix}$

In the formula, Lb_(r,m) denotes a length of he flow path region “r”divided by the electromotive portion unit “m”. Further, it is requiredto average the effective fuel concentrations supplied from the flow pathin the electromotive portion unit “m”, in “s” flow path regions passingthrough the electromotive portion unit.“m”. The effective fuelconcentration supplied to this electromotive portion unit “m” may bethought to depend on a length obtained by averaging Zb_(r,m) defined inaccordance with Formula (10) with respect to “s” flow path regions. Aneffective length Z_(m) between this electromotive portion unit “m” andthe flow path supply port is defined in accordance with Formula (11).

$\begin{matrix}{Z_{m} = {\frac{1}{s}{\sum\limits_{i = 1}^{s}\; Z_{b_{r,m}}}}} & (11)\end{matrix}$

Further, what is the most ideal is that all values of Lb_(r,m) aredesigned to the identical length, and distribution of the flow paths maybe carried out. If all the values Lb_(r,m) set to the identical lengthare defined as L_(e), a formula obtained by substituting Formula (10)for Formula (11) can be rewritten as in Formula (12) below.

$\begin{matrix}{\left\langle Z_{m} \right\rangle = {L_{e}\frac{1}{s}{\sum\limits_{i = 1}^{s}\; b_{i,m}}}} & (12)\end{matrix}$

In the formula, <Z_(m)> denotes an average of Lb_(r,m) values in an“m”-th electromotive portion unit when all the values Lb_(r,m) aredefined as L_(e). Further, when a length obtained by averaging thevalues <Z_(m)> with respect to “n” electromotive portion units, <Z> isdefined as Formula (13). When calculation is actually executed, it isindicated that the calculated value is given in accordance with Formula(14).

$\begin{matrix}{\left\langle Z \right\rangle = {\frac{1}{n}{\sum\limits_{m = 1}^{n}\;\left\langle Z_{m} \right\rangle}}} & (13) \\{\left\langle Z \right\rangle = {L_{e}\frac{{sn} + 1}{2}}} & (14)\end{matrix}$

Further, when a length obtained by multiplying the number “sn (=h)” ofall flow path regions for L_(e) is expressed as a full length of aneffective flow path by using L₀, L_(e) can be written as in Formula(15). Further, <Z> defined in accordance with Formula (15) can bewritten into Formula (16).

$\begin{matrix}{L_{e} = \frac{L_{0}}{s\; n}} & (15) \\{\left\langle Z \right\rangle = \frac{L_{0}\left( {h + 2} \right)}{2h}} & (16)\end{matrix}$

If the average <Z_(m)> of the effective length from the flow path supplyport in all the electrode units “m” meets an inequality of Equation (17)described later, a difference between <Z_(m)> and <Z_(m′)> with respectto arbitrary electromotive portion units m and m′ is within 10% of <Z>.Therefore, as can be seen from the above discussion, a concentrationdifference on an electromotive portion unit by unit basis is also within10% of the average value of the fuel concentrations supplied in “n”electromotive portion units. This denotes that the outputs obtained fromall the electromotive portion units are substantially equal to eachother, and a fuel cell power generator with its stable high output canbe provided.

$\begin{matrix}{{{\left\langle Z_{m} \right\rangle - \left\langle Z \right\rangle}} \leq {\frac{1}{20}\left\langle Z \right\rangle}} & (17)\end{matrix}$

$\begin{matrix}\begin{matrix}{{{\left\langle z_{m} \right\rangle - \left\langle z_{m^{\prime}} \right\rangle}} \leq {{{\left\langle z_{m} \right\rangle - \left\langle z \right\rangle}} + {{\left\langle z_{m^{\prime}} \right\rangle - \left\langle z \right\rangle}}}} \\{\leq {{\frac{1}{20}\left\langle z \right\rangle} + {\frac{1}{20}\left\langle z \right\rangle}}} \\{= {\frac{1}{10}\left\langle z \right\rangle}}\end{matrix} & (18)\end{matrix}$

Now, a description will be given with respect to forming of anelectromotive portion unit of a direct type methanol fuel cell. An anodecatalyst (Pt:Rt=1:1) carrier carbon-black and a cathode catalyst (Pt)carrier carbon black were formed in accordance with a publicly knownprocess (R. Remakumar et al. J. Power Sources 69 (1997) 75). Thecatalyst carrier amounts of the anode and cathode were defined as 30 and15 in percent by weight with respect to carbon 100, respectively.

A perfluorocarbon sulfonic acid solution (Nafion solution SE-20092available from Dupont Co., Ltd.) and ion exchange water were added tothe anode catalyst carrier carbon black formed in the foregoing process,the catalyst carrier carbon black was dispersed, and a paste wasprepared. The paste of 550 μm was applied onto a water repellentprocessed carbon paper TGPH-120 (available from E-TEK) which is an anodecollector, the applied paste was dried, and an anode catalyst layer wasformed, whereby an anode electrode was obtained.

A perfluorocarbon sulfonic acid solution (Nafion solution SE-20092available from Dupont Co., Ltd.) and ion exchange water were added tothe cathode catalyst carrier carbon black formed in the foregoingprocess, the catalyst carrier carbon black was dispersed, and a pastewas prepared. The paste of 225 μm was applied onto a water repellentprocessed carbon paper TGPH-120 (available from E-TEK) which is acathode collector, the applied paste was dried, and a cathode catalystlayer was formed, whereby a cathode electrode was obtained.

A perflourocarbon sulfonic acid film (Nafion 117 available from DupontCo., Ltd.) commercially available as an electrolyte film was disposedbetween the anode catalyst layer of the anode electrode and the cathodecatalyst layer of the cathode layer, and a hot press (125° C., 5minutes, 50 kg/cm²) was applied thereto, whereby the anode electrode,the electrolyte film, and the cathode electrode were bonded with eachother to obtain an electromotive portion unit. A sectional area of theanode catalyst layer in the electromotive portion unit was 10 cm². Inaddition, after the electromotive portion was cut, when the sectionalarea was observed by using an electron microscope, the thickness L ofthe anode catalyst layer was 105 μm, and the thickness of the cathodecatalyst layer was 50 μm. By this electro microscope observation, it wassuccessfully verified that a bonding state among the anode electrode,the electrolyte film, and the cathode electrode was good.

Now, a description will be given with respect to evaluation of theformed electromotive portion unit. The formed electromotive portion unitwas mounted on an evaluation separator, and evaluation of a currentvoltage characteristic was carried out while a temperature wasmaintained at 70° C. Note that measurement was carried out under anoperating condition in which a methanol aqueous solution flow rate isdefined as 0.01 cm/min, an air flow rate is defined as 10 cm/min, amethanol aqueous solution concentration is within the range of 0.5M,1.0M, 1.25M, 1.5M, 1.75M, 2.0M, and 2.5M. As a result, a result whichwas substantially similar to the current voltage characteristic obtainedin FIG. 4 was obtained. After it was verified that the substantiallysimilar current voltage characteristic can be obtained by a similarevaluation method, 100 electromotive portion units of 10 cm² insectional area were formed, and the thus formed electromotive portionunits were used for testing in the embodiments of the present invention.

Second Embodiment

FIGS. 6A to 6C are views each showing essential portions of a directtype methanol fuel cell power generator 200 according to a secondembodiment of the present invention. FIG. 6A is a bottom view showing aninsulating flow path plate 201 positioned at the shown top side. FIG. 6Bis a sectional view viewed in a direction indicated by the arrow, theview being taken along the line β1-β1 in FIG. 6A. FIG. 6C is a sectionalview viewed in a direction indicated by the arrow, the view being takenalong the line β2-β2 in FIG. 6A.

In FIGS. 6A to 6C, reference numeral 201 designates an insulating flowpath plate (fuel side); 202 designates an insulating flow path plate(oxidizing agent side); 203 designates a fuel flow path; 204 designatesa fuel flow path supply port; 205 designates a fuel flow path ejectionport; 206 designates a flow path cap body of a back face of a flow path;207 designates a resin based sealing member; 208 a and 208 b eachdesignate an electromotive portion unit; 209 designates an air flowpath; 210 designates a flow path portion bent to the side of the flowpath cap body 206 such that a flow path does not face the electromotiveportion units 208 a and 208 b; and 211 designates a metallic thin filmfor leading out a current. In addition, the electromotive portion units208 a and 208 b each employ the above-described structure shown in FIG.58. The fuel flow path 203 is provided as an example when twoelectromotive portion units 208 a and 208 b flow alternatively(hereinafter, the structure of such a flow path is referred to as an“alternating type flow path”).

In the direct type methanol fuel cell power generator 200, a fuel issupplied from the fuel flow path supply port 204 into a system. A fuelflow path is formed in the electromotive portion units 208 a and 208 bso as to supply the fuel alternately. The fuel is ejected from the fuelflow path ejection port 205. On the other hand, an oxidizing agent flowsthrough the fuel flow path 209, and power is generated on a surface ofan electromotive portion unit. In this embodiment, the fuel flow path203 supplies a fuel to the electromotive portion unit 208, and then,supplies the fuel to the electromotive portion unit 208 b. Further, thefuel returns to the electromotive portion unit 208 a. Then, while thefuel is supplied alternately to the electromotive portion units 208 aand 208 b, the fuel is ejected from the fuel flow ejection port 205. Thefuel flow path 203 is thus configured, whereby the fuel can be suppliedsubstantially uniformly and constantly to the electromotive portionunits 208 a and 208 b. Thus, its output becomes further stable.

In this embodiment, it is desirable that a return count “s” of the flowpath is an even number and great in order to easily meet the conditionof Formula (2). In the case where the return count is an odd number, asthe count “s” increases, a difference between <Z_(m)> and <Z> isreduced, and thus, it is desirable that the count “s” is equal to orgreater than 5 in particular.

In the above-described two embodiments, although an example of twoelectromotive portion units is shown, stability of a power generationoutput can be improved by a similar technique also in a power generatorhaving three or more electromotive portion units.

Furthermore, an example of such a flow path shape as to meet thecondition of Formula (2) is shown in FIGS. 7A to 7D, FIG. 8, FIGS. 9Aand 9B, and FIGS. 10A to 10C. In these figures, reference numeral 271designates a flow path plate; 272 designates a portion at which anelectrode portion in an electromotive portion unit is disposed; 273 and274 designate a supply port and an ejection port of a flow path; and 275designates a flow path. In FIGS. 10A to 10C, two electromotive portionunits are arranged on each of both faces of the flow path plate. Then, afuel or oxidizing agent is supplied alternately to electromotive portionunits on both faces via the penetrating port 276 penetrating both facesof the flow path.

Even in the case where a distance between the divided flow paths isremarkably different from another, a rate of a length to an average offlow path widths in the whole flow path may be substituted to beconverted by multiplying it on a region by region basis. For example,even in the case where a portion at which the flow path is returned isdisposed at the inside instead of the outside in the range of theelectrode portion as in FIG. 5A, the flow path can be allocated bypartitioning it as shown in FIG. 5C.

Further, in a flow path plate for supplying a fuel or oxidizing agent toelectromotive portion units arranged on both faces of such a flow pathplate as used for a mono-polar type flow path plate, advantageous effectof the structure of the flow path described in the present embodimentcan be achieved as in Example 7 or the like described later.

EXAMPLE 1

A power generation test under the following condition was carried outwith respect to the direct type methanol fuel cell power generator 100described above. That is, an initial concentration of a methanol aqueoussolution fuel was defined as 3 mol/l; a flow path plate temperature wasdefined as 70° C.; a fuel flow rate was defined as 0.02 cm/min; and anair flow rate was defined as 20 cm/min. Hereinafter, this condition isreferred to as an operating condition of Example 1.

FIG. 11 is a view showing a result of a current voltage characteristicof the direct type methanol fuel cell power generator 100. As can beseen from FIG. 11, it was observed that a critical charge current in anelectromotive portion unit at the side of the flow path supply port wasabout 95 mA/cm² and that an electromotive current unit at the side ofthe flow path ejection port was 77 mA/cm². Therefore, in the case whereboth of them were electrically connected to each other in series, acharge current of 77 mA/cm² was substantially obtained. As compared witha case in which a conventional serial type flow path of ComparativeExample 1 described later was used, it was verified the critical chargecurrent density was improved by about 10%. This indicates that the flowpath plate 101 supplies a fuel better as compared with the conventionalserial type flow path.

EXAMPLE 2

FIG. 12 shows a result obtained by measuring a current voltagecharacteristic under the operating is condition of Example 1. As shownin FIG. 12, it was found that a value of the critical charge currentdensity of an electromotive portion unit 1 at the side of the flow pathsupply port was about 90 mA/cm² and that a value of an electromotiveportion unit 2 at the side of the flow path ejection port was about 87mA/cm². Therefore, in the case where both of them were electricallyconnected to each other in series, a charge current of 87 mA/cm² wassubstantially obtained. As compared with a case in which theconventional serial type flow path of Comparative Example 1 describedlater was used, it was verified that the critical charge current densitywas improved by about 24%. In addition, in the flow path plates in thisExample and Example 1, the lengths of eight flow path regionsefficiently divided were all equal to each another. In this Example,<Z₁>−<Z₂>=0, and the condition of Formula 1 is met. However, in Example1, |<Z>−<Z_(m)>|=1/5<Z>, and the condition is not met. That is, the flowpath plate used in Example 2 is designed so as to meet Formula (1), andthus, it is considered that the critical charge current density has beenimproved more remarkably than the flow path plate formed in Example 1.

Comparative Example 1

A direct type methanol fuel cell power generator was configured as shownin FIGS. 13A to 13C by providing two electromotive portion units, andemploying the conventional serial type flow path. In FIGS. 13A to 13C,like functional portions in FIG. 6 are designated by like referencenumerals. A detailed description of these functional portions is omittedhere.

In Comparative Example 1, a parallel type flow path was used as a flowpath 280 for supplying an oxidizing agent. A power generation test of astack portion of Comparative Example 1 was carried out under theoperating condition of Example 1. As a result, a current voltagecharacteristic shown in FIG. 14 was obtained. As is seen in FIG. 14, avalue of the critical charge current density of the electromotiveportion unit 208 a at the side of the flow path supply port was about100 mA/cm², and a value of the electromotive portion unit 208 b at theside of the flow path ejection port was about 70 mA/cm². Therefore, inthe case where both of them were electrically connected to each other inseries, only a charge current of 70 mA/cm² was obtained.

Comparative Example 2

A direct type methanol fuel cell power generator was configured as shownin FIGS. 15A to 15C by providing two electromotive portion units, andemploying the conventional parallel type flow path. In FIGS. 15A to 15C,like functional portions in FIGS. 6A to 6C are designated by likereference numerals. A detailed description of these functional portionsis omitted here.

This fuel cell power generator was powered ON in an operating conditionof Example 1. As a result, a current voltage characteristic shown inFIG. 16 was obtained. FIG. 16 shows that two electromotive portion unitswere used as an electrically serial circuit, a charge current of 75mA/cm² was obtained, and a change after elapse of time was tracked.

In addition, FIG. 16 shows a charge current characteristic in the casewhere a fuel cell power generator using the flow path plate of Example 2has been operated. A regular fine fluctuation in both plots of FIG. 16is caused by a temperature controller. It was seen from FIG. 16 that,when the conventional parallel type flow path was used, the instabilityof an output due to a deflection in a fuel supply amount with respect totwo electromotive portion units occurred. In the case where the flowpath plate formed in Example 2 was used, it was found that a stableoutput was obtained irrespective of an operation time. As a result, inthe conventional parallel type flow path, no stable output was obtainedbecause a fuel did not flow constantly at a branched portion of a pipe.However, by using the flow path plate of the present invention, a fuelcan be supplied uniformly because no pipe branching occurs. Thisindicates that a stable output can be obtained.

Comparative Example 3

FIG. 17 is a view showing a result of a power generation test inComparative Example 3. In Comparative Example 3, although a flow path isformed in the same manner as the flow path plate formed in Example 2,there was formed a flow path in which an effective full length of theflow path passing through the side of the electromotive portion unit 2was shorter by 20% with respect to an effective full length of the flowpath passing through the side of the electromotive portion unit 1, and amethanol fuel cell power generator comprising two electromotive portionunits was configured.

As compared with FIG. 12 in Example 2, it is found that a difference incritical charge current-density between both of the electromotiveportion units is remarkable. This is because effective flow path lengthsof which two electromotive portion units pass are different from eachother. This is also because, even if a flow path shape was used suchthat the average methanol concentrations supplied from the fuel flowpath to the electromotive portion units each are equal to each another,absolute amounts of methanol supplied to each of the electromotiveportion units are different from each another by 20%. Therefore, as wasassumed when Formula (1) is derived, in addition, an effective length ofa flow path region divided by each of the electromotive portion unitsshould be configured to be equal to another in order to facilitate flowpath design.

As described above, according to the direct type methanol fuel cellpower generator 300 of the present embodiment, a deflection in outputson an electromotive portion unit by unit basis is reduced and stablefuel supply can be carried out. Thus, a stable output can be obtained.

Third Embodiment

FIG. 18 is a side view showing a direct type methanol fuel cell powergenerator 300 according to a third embodiment of the present invention.FIGS. 19A and 19B are views each showing the direct type methanol fuelcell power generator 300. FIG. 19A is a schematic view showing the powergenerator, and FIG. 19B is a transverse cross section showing the powergenerator. FIGS. 20A to 20E are exploded views each showing the directtype methanol fuel cell power generator 300. These figures are alsosectional views showing the power generator.

In the direct type methanol fuel cell power generator 300, a stack bodyis stacked with a first flow path plate 310, a first electromotiveportion layer 320, a second flow path plate 330, a second electromotiveportion layer 340, and a third flow path plate 350 from the upper middleof FIG. 18. This stack body is sandwiched between thick plates 360 and361 made of a stainless material, and is formed by tightening it with abolt 362. Reference numerals 370 to 373 each designate a metallicterminal, and the terminals are connected to carbon materials 311 and351, respectively. Further, reference numeral 374 designates a copperwire, wherein the metallic terminal 371 and the metallic terminal 372are made conductive to each other.

The first flow path plate 310 is integrally molded so as to insulate twosquare shaped carbon materials 311 with a thermosetting type epoxy resin312. The area and shape of the carbon material 311 are identical tothose of an electromotive portion unit to be arranged as describedlater. In addition, on the bottom face, a first flow path 313 for fuelis formed, in the shape of a recessed groove. Further, a fuel supplyport 314, a fuel ejection port 315, an oxidizing agent supply port 316,and an oxidizing agent ejection port 317 are formed, and pipes 318 a to318 d are connected thereto, respectively.

The first electromotive portion layer 320 comprises: two sets ofelectrolyte films 321 configuring electromotive units; an anodeelectrode 322 including an anode catalyst layer provided so as tosandwich these electrolyte films 321 and a cathode electrode 323including a cathode catalyst layer; and a silicon rubber resin basedsealing member 324 sandwiching these electrodes. The anode electrode 322is disposed at the upper side in the figure, and the cathode layer 323is disposed at the lower side in the figure.

The silicon rubber resin based sealing member 324 is formed by cuttingthe supply port and the ejection port of the flow path and the electrodeportion of the electromotive portion unit in order to prevent a fuel oran oxidizing agent from leaking from a side face of the flow path orelectromotive portion unit. The thickness of the silicon rubber resinbased sealing member 324 used is larger by 0.1 mm than that of the anodeelectrode 322 and cathode electrode 323, and the electrolyte film 321 issandwiched between them.

Moreover, an interval between the anode electrodes 322 arranged inparallel and an interval between the cathode electrodes 323 arranged inparallel were identical to a distance between the two carbon materials311 of the first flow path plate 310.

The second flow path plate 330 is a bipolar type flow path plate, and isintegrally molded so as to insulate two square shaped carbon materials331 with a thermosetting epoxy resin 332. The area and shape of thecarbon material 331 are identical to those of electromotive portionunits arranged as described later. In addition, on the top face, asecond flow path 333 for oxidizing agent is formed in the shape of arecessed groove, and on the bottom face, a third flow path 334 for fuelis formed in the shape of a recessed groove.

Two electromotive portion units are provided in the second electromotiveportion layer 340. The second electromotive portion layer 340 comprises:two sets of electrolyte films 341 configuring electromotive portionunits; an anode electrode 342 including an anode catalyst layer providedso as to sandwich these electrolyte films 341 and a cathode layer 343including a cathode catalyst layer; and a silicon rubber resin basedsealing member 344 sandwiching these electrodes. The anode electrode 342is disposed at the upper side in the figure, and the cathode electrode343 is disposed at the lower side in the figure.

The silicon rubber resin based sealing member 344 is formed by cuttingthe supply port and the ejection port of the flow path and the electrodeportion of the electromotive portion unit in order to prevent a fuel oran oxidizing agent from leaking from a side face of the flow path or theelectromotive portion unit. The thickness of the silicon rubber resinbased sealing member 344 used is larger by 0.1 mm than that of the anodeelectrode 342 and cathode electrode 343, and the electrolyte film 341 issandwiched between them.

In addition, an interval between the anode electrodes 342 arranged inparallel and an interval between the cathode electrodes 343 arranged inparallel were identical to a distance between the two carbon materials311 of the first flow path plate 310.

The third flow path plate 350 is integrally molded so as to insulate twosquare shaped carbon materials 351 with a thermosetting type epoxy resin352. The area and shape of the carbon material 351 are identical tothose of the electromotive portion units arranged. In addition, on thetop face, a fourth flow path 353 for oxidizing agent is formed in theshape of a recessed groove.

The fuel supplied from a fuel pump (not shown) is supplied to the fuelsupply portion 314 via the pipe 318 c. The supplied fuel is dischargedfrom the fuel ejection port 315 to the outside of the cell through thefirst flow path 313 and the third flow path 334 via the pipe 318 d. Thatis, a fuel is supplied to the anode electrodes 322 and 342. In addition,the oxidizing agent supplied from an air pump (not shown) is supplied tothe oxidizing agent supply port 316 via the pipe 318 a. Then, thesupplied oxidizing agent is discharged from the oxidizing agent ejectionport 317 to the outside of the cell through the first flow path 335 andthe third flow path 353 via the pipe 318 b. That is, the fuel issupplied to the anode electrodes 323 and 343.

EXAMPLE 3

In the direct type methanol fuel cell power generator 300 as describedabove, if a fuel and an oxidizing agent are supplied, four electromotiveportion units are electrically connected in series, and thus, anelectrical output is obtained from the metallic terminals 370 and 373 bymeans of an electron charge device. Note that a gold wire of 0.1 mm indiameter was brought into contact with the anode electrode and thecathode electrode on an electromotive portion unit by unit basis, andwas led out to the outside of a stack. A voltage on an electromotiveportion unit by unit basis was measured.

Operation of the direct type methanol fuel cell power generator 300 issubstantially identical to the operating condition of Example 1.However, supply amounts of the oxidizing agent and fuel were doubled bytwo times of Example 2 in the number of electromotive portion units.That is, the initial concentration of a methanol aqueous solution fuelwas defined as 3 mol/l; a flow path-plate temperature was defined as 70°C.; a fuel flow rate was defined as 0.04 cm/min; and an air flow ratewas 40 cm/min. Hereinafter, this operating condition is referred to asan operating condition of Example 3.

FIG. 21 is a view showing a current voltage characteristic of theabove-described direct type methanol fuel cell power generator 300. Asis seen from FIG. 21, there are shown that an output difference betweenthe electromotive portion units arranged in parallel in a planardirection is small, and that constant fuel supply is carried out ascompared with a conventional serial type flow path and a conventionalparallel type flow path of Comparative Example 4 and Comparative Example5 described later.

However, a remarkable difference in value of the critical charge currentdensity occurred between sets of the electromotive portion unitsdisposed at the top and bottom. This is because a pipe is branched intotwo sections from the fuel supply port and the oxidizing agent supplyport of a stack, whereby a fuel or an oxidizing agent is supplied to thesets of the top and bottom electromotive portion units, and thus, thefuel and oxidizing agent are not supplied uniformly to the sets of thetop and bottom electromotive portion units.

Comparative Example 4

FIGS. 22A to 22C are views showing flow path plates 391 to 393 havingformed thereon serial type flow paths incorporated in a direct typemethanol fuel cell power generator comprising four electromotive portionunits. FIG. 23 is a view showing a test result concerning a stack ofComparative Example 4. The flow path plate 392 is of bipolar type. InFIGS. 22A to 22C, like functional portions shown in FIGS. 20A to 20E aredesignated by like reference numerals. A detailed description of thesefunctional portions is omitted here.

In Comparative Example 4, it was found that a value of the criticalcharge current density observed by the electromotive portion unit at theside of the ejection portion was lowered by about 30% as compared with avalue of the critical charge current density obtained from theelectromotive portion unit at the side of the fuel supply port. Withrespect to the sets of the top and bottom electromotive portion units aswell, it was found that a remarkable difference occurred with thecritical charge current values. This result is considered to haveoccurred because the conventional serial type flow path is employed inthe shape of the flow path and because the pipe is branched in avertical direction.

Comparative Example 5

FIG. 24 and FIGS. 25A to 25E are views showing flow path plates 393 to395 having formed thereon parallel type flow paths incorporated in adirect type methanol fuel cell power generator comprising fourelectromotive portion units according to Comparative Example 5. In thesefigures, like functional portions in FIGS. 20A to 20E are designated bylike reference numerals. A detailed description of these functionalportions is omitted here. The flow path plate 394 is of bipolar type.

A parallel type was used as a flow path shape, and thus, the width inthe short side direction of the flow path plates 393 to 395 was slightlyincreased by a branched pipe. Concurrently, the widths of theelectrolyte films 321 and 341 of the electromotive portion units andthose of the silicon rubber resin based sealing members 324 and 344 wereincreased similarly.

FIG. 26 is a view showing a result obtained by measuring a currentvoltage characteristic under the operating condition of Example 3 withrespect to the thus configured direct type methanol fuel cell powergenerator. As is seen from this figure, voltages became unstable withrespect to all the electromotive portion units and a remarkabledifference in critical charge current occurred with respect to the setsof the top and bottom electromotive portion units as well. This resultis considered to have occurred because uniform fuel supply at a pipebranching portion was not carried out in the conventional parallel typeflow path.

As has been described above, in the direct type methanol fuel cell powergenerator 300 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Fourth Embodiment

FIG. 27 is a side view showing a direct type methanol fuel cell powergenerator 400 according to a fourth embodiment of the present invention.FIGS. 28A to 28C are plan views showing flow path plates 410, 430, and450 of the direct type methanol fuel cell power generator 400. Thesefigures are sectional views showing the above plates.

In the direct type methanol fuel cell power generator 400, a stack bodyis stacked with the first flow path plate 410; a first electromotiveportion layer 420, the second flow path plate 430, a secondelectromotive portion layer 440, and the third flow path plate 450 fromthe upper middle of FIG. 27. This stack body is sandwiched between thickplates 460 and 461 made of a stainless material, and is formed bytightening it with a bolt 462. Reference numerals 470 to 473 eachdesignate a metallic terminal. Further, reference numeral 474 designatesa copper wire, wherein the metallic terminal 471 and the metallicterminal 472 are made conductive.

The first flow path plate 410 is formed of an acrylic resin, and goldribbons 411 and 412 of 20 μm in thickness and 2 mm in width are providedon a surface of the plate. In addition, on the bottom face, a first flowpath 413 for fuel is formed in the shape of a recessed groove. Further,a fuel supply portion 414, a fuel ejection port 415, an oxidizing agentsupply port 416, and an oxidizing agent ejection port 417 are formed,and pipes 418 a to 418 d are corrected thereto, respectively.

The gold ribbons 411 and 412 are disposed at a substantial center ofeach electromotive portion unit in order to capture a current from eachelectromotive portion unit. In addition, these ribbons are disposed atthe top face, one side face, and the bottom face of the flow path plate410 so as to obtain a positional relationship vertical to a current flowdirection in the flow path 413. The above-described gold ribbons 411 and412 are wound around the top and bottom of the first flow path plate 410through the side face, thereby making it possible to establish anelectrical serial state of electromotive portion units.

Another conductive member may be used instead of the gold ribbons 411and 412. For example, it is desirable to use a material such asplatinum, ruthenium, rhodium, or iridium. In the case where a base metalis used as a substrate, the substrate can be substituted by covering itwith the above-described precious metal of about 10 μm in thickness ontitanium or the like.

The first electromotive portion layer 420 is configured in the samemanner as the first electromotive portion layer 320 of theabove-described methanol fuel cell power generator 300. Thus, a detaileddescription of the layer is omitted here.

The second electromotive portion layer 430 is a flow path plate ofbipolar type, and is formed of an acrylic resin. On a surface of thelayer, gold ribbons 431 and 432 of 20 μm in thickness and 2 mm in widthare provided. On the top face of the layer, a second flow path 433 foroxidizing agent is formed in the shape of a recessed groove, and on thebottom face thereof, a third flow path 434 for fuel is formed in theshape of a recessed groove.

The gold ribbons 431 and 432 are positioned at a substantial center ofeach electromotive portion unit in order to capture a current from eachelectromotive portion unit. In addition, these ribbons are disposed atthe top face, one side face, and the bottom face of the flow path plate430 so as to obtain a positional relationship vertical to a currentflowing direction in the flow paths 433 and 434. That is, the goldribbons 431 and 432 are wound around the top and bottom of the secondflow path plate 430 through the side face, thereby making it possible toestablish an electronic serial state between the electromotive portionunits.

The second electromotive portion layer 440 is configured in the samemanner as the second electromotive portion layer 340 of theabove-described direct type methanol fuel cell power generator 300.Thus, a detailed description of this layer is omitted here.

The third flow path plate 450 is formed of an acrylic resin, and on asurface of the plate, gold ribbons 451 and 452 of 20 μm in thickness and2 mm in width are provided. On the top face, a fourth flow path 453 foroxidizing agent is formed in a recessed groove. The above-described goldribbons 451 and 452 are wound around the top and bottom of the thirdflow path plate 450 through the side face, thereby making it possible toestablish an electrical serial state between the electromotive units.

In the thus configured direct type methanol fuel cell power generator400, a fuel and an oxidizing agent are supplied or discharged in thesame manner as the above-described direct methanol fuel cell powergenerator 300. Then, four electromotive power units are electricallyconnected in series, and thus, an electrical output is obtained from themetallic terminals 470 and 473 by means of an electron charge device.

EXAMPLE 4

FIG. 29 is a view showing a current voltage characteristic when theabove-described direct type methanol fuel cell power generator 400 hasbeen operated under the operating condition of Example 3. As shown inFIG. 29, in Example 4, it is found that a stable output can be obtainedas compared with a case in which a conventional serial flow path typeand a conventional parallel type flow path of Example 5 and Example 6described later have been used. This result indicates that constant fuelsupply is carried out.

Further, a result of the current voltage characteristic is identical toa test result (FIG. 21) of Example 3 in which measurement has beencarried out with respect to a stack portion at which the same flow pathstructure has been formed of a carbon material. Even by bringing aconductive member into contact with only a part of an electromotiveportion, it was successfully demonstrated possible to make a powergenerating operation which is not inferior to a case in which the carbonmaterial is used. Further, this demonstrates that a portion at which aconductive portion comes into contact with an electrode may not alwaysbe in the range as wide as possible all over the electrode in order toinduce an electronic output from an electromotive portion unit, i.e.,that a current can be sufficiently captured merely by partiallyarranging a conductive member. In particular, this indicates that thepresent invention can be fully applied to a cell power generator forfuel or the like for small sized portable electronic device which doesnot require an output at a mass current.

Moreover, as in the conventional stack structure, in the case of forminga flow path plate in which a carbon material is molded integrally withan insulating resin, it can be considered that a dislocation betweenmembers or a gap between flow paths due to a difference in hardnessoccurs when the carbon material and insulating resin are integrated witheach other. In the case where a carbon-resin composite material whichcan be molded with a die suitable to mass production is used as anelectrically conductive portion, a heat expansion rate with theperipheral insulating resin member, a difference in deformationtemperature or the like must be considered. Even when a flow path isformed by cutting it after being integrally molded, there is a need touse a tool with high hardness because the carbon material is partiallycontained.

However, in the case where a bipolar type flow path plate is formedmerely of a resin free of a carbon material, such a bipolar flow pathplate may be merely formed in only one process for injection moldingwhich has been carried out conventionally. Further, an advantage of thebipolar type flow path plate that wiring is simplified due to anelectrical serial structure in a stacking direction is reduced in thecase of a portable electronic device fuel cell in which reduction inthickness is important. Therefore, it is important to develop means forobtaining insulation between flow path plates for arrangingelectromotive portion units in the same planar direction. In thisrespect, by using the flow path plate in the present embodiment, thereis no need to form a complicated flow path plate on which conductiveportions and an insulating portion for insulating them from each otherare integrally molded. Further, the easiness of molding properties byusing a resin, i.e., easy reduction in thickness becomes furtherpossible.

As has been described above, in the direct type methanol fuel cellbattery power generator 400 according to the present embodiment, adeflection in output on an electromotive portion unit by unit basis isreduced and stable fuel supply can be carried out. Thus, a stable outputcan be obtained.

Fifth Embodiment

FIGS. 30A to 30C are views showing first to third flow path plates 510,530, and 550 incorporated in a direct type methanol fuel battery cellpower generator 500 (not shown) according to a fifth embodiment of thepresent invention. As a material for each flow path plate, an acrylicresin being an insulating resin was used. The power generator wasconfigured by using bipolar type flow path plates 510, 530, and 550 eachcomprising a conventional serial type flow path shaped in the same wayas in the case of Comparative Example 4. In the figures, referencenumerals 511, 512, 531, 532, 551, and 552 designate gold ribbonsdisposed in the same manner as in Example 4, and reference numerals 513,533, 534, and 553 designate flow paths.

EXAMPLE 5

FIG. 31 is a view showing a current voltage characteristic when theabove-described direct type methanol fuel cell power generator 500 hasbeen operated under the operating condition of Example 3. Also inExample 5, the same output characteristic as that shown in ComparativeExample 4 was obtained. That is, it was successfully demonstratedpossible to make a power generating operation which was not inferior toa case in which a carbon material was used, merely by forming the flowpath plates 510, 530, and 550 of an insulating resin member and bringinga conductive member into contact with only a portion of an electromotiveportion.

However, it was found that the critical charge current density of theelectromotive portion unit at the side of the fuel ejection port islowered by 30% as compared with the critical charge current density ofthe electromotive portion unit at the side of the fuel supply port. Thislowering was observed in a test result (refer to FIG. 23) concerning thestack of Comparative Example 4, and is considered to be produced becauseof the presence of the flow path structure, not because of the presencethe material for flow path plate.

As has been described above, in the direct type methanol fuel cell powergenerator 500 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Sixth Embodiment

FIGS. 32A and 32B are views each showing a direct type methanol fuelcell power generator 600 according to a sixth embodiment of the presentinvention. FIG. 32A is a longitudinal cross section showing the powergenerator. FIG. 32B is a sectional view viewed in a direction indicatedby the arrow, the sectional view being taken along the line γ-γ in FIG.32A. FIGS. 33A to 33C are views showing first to third flow path plates610, 630, and 650 incorporated in the direct type methanol fuel cellpower generator 600.

The direct type methanol fuel cell power generator 600 is formed to bestacked with the first flow path plate 610, a first electromotiveportion layer 620, the second flow path plate 630, a secondelectromotive portion layer 640, and the third flow path plate 650 inupward order in FIGS. 32A and 32B.

An acrylic resin being an insulating resin was used as a member of aflow path plate, and a flow path plate whose flow path is of paralleltype and is formed in a stripe shape, which is identical in the case ofComparative Example 5, was used. A conductive member was arranged in thesame manner as in Example 4.

An acrylic resin being an insulating resin was used as a material foreach flow path plate. The power generator was configured by usingbipolar type flow path plates 610, 630, and 650 comprising theconventional serial type flow paths which are shaped in the same manneras in the case of Comparative Example 4. In the figure, referencenumerals 611, 612, 631, 632, 651, and 652 each designate a gold ribbon;and reference numerals 613, 633, 634, and 653 each designate a flowpath. The gold ribbons 611, 612, 631, 632, 651, and 652 are disposedalong long sides of the flow path plates 610, 630, and 650.

The first electromotive portion layer 620 is configured in the same wayas in the first electromotive portion layer 320 of the above-describeddirect type methanol fuel cell power generator 300. A detaileddescription is omitted here. The second electromotive portion layer 640is configured in the same way as in the second electromotive portionlayer 340 of the above-described direct type methanol fuel cell powergenerator 320. Thus, a detailed description is omitted here.

EXAMPLE 6

FIG. 34 is a view showing a current voltage characteristic when theabove-described methanol fuel cell power generator 600 has been operatedunder the operating condition of Example 3. As is seen from FIGS. 3A and3B, the same output characteristic as that shown in Comparative Example5 can be obtained. That is, it was successfully demonstrated possible tomake a power generating operation which was not inferior to a case inwhich a carbon material was used, merely by forming a flow path of aninsulating resin member and bringing a conductive member into contactwith only a part of an electromotive portion.

However, likewise in a case shown in Comparative Example 2 andComparative Example 5, it was observed that an output was unstable dueto a deflection in a fuel supply amount with respect to twoelectromotive portion units arranged on the same plane. This instabilityis considered to be produced because of the presence of the flow pathstructure, not because of use of an acrylic material.

As has been described above, in the direct type methanol fuel cell powergenerator 600 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus a stable output can beobtained.

Seventh Embodiment

FIG. 35 is a side view showing a direct type methanol fuel cell powergenerator 700 according to a seventh embodiment of the presentinvention. FIGS. 36A and 36B are views each showing the direct typemethanol fuel cell power generator 700. FIG. 36A is a perspective viewshowing the power generator. FIG. 36B is a sectional view showing thepower generator. FIGS. 37A to 37C are views showing first to third flowpath plates 710, 730, and 750 incorporated in the direct type methanolfuel cell power generator 700.

An acrylic resin being an insulating resin was made of a material, and amono-polar type flow path plate having an alternate type flow path shapewas used. In the direct type methanol fuel cell power generator 700, astack body is stacked with the first flow path plate 710, a firstelectromotive portion layer 720, the second flow path plate 730, asecond electromotive portion layer 740, and the third flow path plate750 in the upper middle of FIG. 36. The stack body is sandwiched betweenthick plates 760 and 761 made of a stainless material, and is formed bytightening it with a bolt 762. Reference numerals 770 a and 770 h eachdesignate a metallic terminal.

The first flow path plate 710 comprises gold ribbons 711 and 712. On thebottom face, a first flow path 713 for oxidizing agent is formed in theshape of a recessed groove. Further, a oxidizing agent supply port 714,a oxidizing agent ejection port 715, an fuel supply port 716, and anoxidizing agent ejection port 717 are formed, and pipes 718 a to 718 dare connected to these ports, respectively.

The anode electrode 723 is disposed at the lower side in the figure, andthe cathode layer 722 is disposed at the upper side in the figure. Theanode electrode 743 is disposed at the upper side in the figure, and thecathode layer 742 is disposed at the lower side in the figure.

The second flow path plate 730 is a mono-polar type flow path plate, andis formed of an acrylic material. A second flow path 733 for fuel isformed in a shape which penetrates in a thickness direction of secondflow path plate. A detailed description of the layer is omitted here.

The third flow path plate 750 comprises gold ribbons 751 and 752. On thetop face, a third flow path 753 for oxidizing agent is formed in theshape of a recessed groove.

Further, reference numerals 771 a to 771 e each denote a copper wire.The copper wire 771 a causes conduction between the metallic terminals770 a and 770 b. The copper wire 771 b achieves conduction between themetallic terminals 770 c and 770 e. The copper wire 771 c achievesconduction between the metallic terminals 770 d and 770 f. The copperwire 771 d achieves conduction between the metallic terminals 770 g and770 i. The copper wire 771 e achieves conduction between the metallicterminals 770 h and 770 j.

The oxidizing agent fed from a fuel pump (not shown) is supplied to theoxidizing agent supply port 714 via the pipe 718 c, and then, thesupplied oxidizing agent is ejected from the oxidizing agent ejectionport 715 through the first flow path 713 and the third flow path 753 tothe outside of the cell via the pipe 718 d. That is, the oxidizing agentis supplied to cathode electrodes 722 and 742. In addition, the fuel fedfrom an air pump (not shown) is supplied to an fuel supply port 716 viaa pipe 718 a, and then, the supplied fuel is ejected from an fuelejection port 717 through the second flow path 733 to the outside of thecell via the pipe 718 b. That is, the fuel is supplied to anodeelectrodes 723 and 743.

In the figure, reference numerals 711, 712, 751, and 752 each designatea gold ribbon, and reference numerals 713, 733, and 753 each designate aflow path. Further, the oxidizing agent supply port 714, the oxidizingagent ejection port 715, the fuel supply port 716, and the fuel ejectionport 717 are formed, and pipes 718 a to 718 d are connected to theseports, respectively.

With respect to the mono-polar type flow path plates positioned amongthe four electromotive portions, a flow path penetrates a flow pathplate on the top and bottom, and a fuel is supplied from the supply portto the flow path. The thickness of the mono-polar type flow path platewas defined to be twice of the depth of the flow path in Example 3 suchthat the depth of the flow path per electromotive portion unit is equalto that of the flow path in Example 3.

The gold ribbons 711, 712, 751, and 752 for inducing an electricaloutput from electromotive portion units each have the thickness andwidth equal to those of Example 4. However, with respect to themono-polar type flow path plate, the top and bottom of the flow pathplate was not rounded in order to ensure an insulated state on the topand bottom. Further, in order to provide electrical wiring among fourgold ribbons of the mono-polar type flow path plate, as shown in FIG.35, the gold wires 771 a to 771 e of 0.1 mm in diameter was insertedbetween each of the gold ribbons 711, 712, 751, and 752 and the siliconrubber resin base sealing member at the end of the flow path plate whena stack is formed.

An electromotive portion unit was installed such that the anodeelectrode faced the mono-polar type flow path plate 730, a fuel wassupplied to the pipe 718 a such that the fuel was supplied to a flowpath with which the anode electrode comes into contact, and an oxidizingagent was supplied from the pipe 718 c. A voltage on an electromotiveportion unit by unit basis was measured by utilizing the gold wireswhich are electrically connected between the electromotive portionunits.

EXAMPLE 7

FIG. 38 is a view showing a current voltage characteristic when theabove-described direct type methanol fuel cell power generator 600 hasbeen operated under the operating condition of Example 3. As in Examples2, 3 and 4, it was verified that advantageous effect of an alternatetype flow path was well achieved. Further, it was found that an outputdifference between the electromotive portion units arranged on the topand bottom of the mono-polar type flow path plate 730 was very small ascompared with that of Examples 3 and 4. This improvement is consideredto have been achieved for the following reason. That is, in the case ofExamples 3 and 4, a fuel was supplied to a set of two electromotiveportion units by the two branched flow paths. In contrast, in Example 7,a fuel was supplied to four electromotive portion units by one flow pathwhich does not branch. That is, in the mono-polar type flow path plate730 as well, it was demonstrated that an alternate type flow path waseffective, and its validity was verified.

In the mono-polar type flow path plate 730, by using the flow path 733which is shaped to penetrate on both faces of the flow path plate, itwas verified possible to make substantially uniform a supply amount ofthe fuel to electromotive portion units arranged on both faces of theflow path plate from this Example and the results of Examples 8 and 11described later. This result indicates validity of claim 4 in thepresent invention. Further, the flow path is shaped so as to be bent andmeandered as represented by the alternate type flow path shown in thisExample or Example 8 described later instead of a parallel type shape,whereby it is found possible to carry out more stable supply of the fueland oxidizing agent.

That is, by using the flow path plate according to the presentembodiment, it becomes possible to flexibly design the shape of the flowpath fully considering operating efficiency of the entire fuel cellpower generator such as a burden of a complementary load due to loweringof a pressure loss in the flow path, prevention of residence of aproduct during power generation, supply of the fuel and oxidizing agent,position of the ejection port and the like. Further, by using the flowpath plate having the alternate type flow path, it was verified possibleto obtain a uniform and stable output in any of a plurality ofelectromotive portion units as shown in this Example.

As has been described above, in the direct type methanol fuel cell powergenerator 700 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Eighth Embodiment

FIGS. 39A to 39C are plan views and sectional views of essentialportions showing a direct type methanol fuel cell power generator 800(not shown) according to an eighth embodiment of the present invention.FIG. 39A shows a first flow path plate 810, FIG. 39B shows a second flowpath plate 830, and FIG. 39C shows a third flow path plate 850.

As in Example 7, an acrylic resin being an insulating resin was used asa member of a flow path plate, a mono-polar type flow path plate asshown in FIG. 35 comprising a serial type flow path was formed, and adirect type methanol fuel cell power generator was configured. In thefigure, reference numerals 811, 812, 831, 832, 851, and 852 eachdesignate a gold ribbon, and reference numerals 813, 833, and 853 eachdesignate a flow path.

EXAMPLE 8

FIG. 40 is a view showing a current voltage characteristic when theabove direct type methanol fuel cell power generator 800 has beenoperated under the operating condition of Example 3. As is seen fromFIG. 40, as in Comparative Example 1, Comparative Example 4, and Example5, the critical charge current density of the electromotive portion unitat the side of the fuel ejection port was lowered by about 30% ascompared with the critical charge current density of the electromotiveportion unit-at the side of the fuel supply port. However, as in Example7, it was verified that an output difference is reduced between twogroups of electromotive portion units arranged on the top and bottom ofthe mono-polar type flow path plate.

As has been described above, in the direct type methanol fuel cell powergenerator 800 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Ninth Embodiment

FIG. 41 is a plan view and a sectional view showing a flow path plate930 incorporated in a direct type methanol fuel cell power generator 900(not shown) according to a ninth embodiment of the present invention.These plan view and sectional view are shown as required.

A mono-polar type flow path 930 was formed by using an acrylic resinbeing an insulating resin. In the figure, reference numeral 933 shows analternate type flow path. In addition, a reinforce member 934 isprovided in the flow path 933. The reinforce member 934 has thethickness by about 75% of the depth of the flow path.

EXAMPLE 9

FIG. 42 is a view comparatively showing current voltage characteristicsin the case where the direct type methanol fuel cell power generator 900and the direct type methanol fuel cell power generator 700 have beencontinuously operated for one hour under a charge current of 75 nA/cm²at 70° C., respectively. From FIG. 42, in the direct type methanol fuelcell power generator 700, it was verified that an irregular fluctuationof a voltage output occurred. In order to clarify the cause of thisfluctuation, a sheet of silicon rubber resin was sandwiched betweenstacks as a dummy of a set of electromotive portion units positioned atthe upper part of a mono-polar type flow path plate, and visualizationof the mono-polar type flow path plate was carried out. As a result, itwas found that a comb-shaped structure portion forming a flow path issignificantly inclined or slightly swung by a tightening pressure in thevertical direction of the flow path plate when a stack is formed andexpansion or the like in the thickness direction of the electromotiveportion unit during operation, and then, air bubbles of carbon dioxideproduced in the flow path of the mono-polar type flow path plate ontowhich a fuel is supplied short-circuits a flow path. In this way, it wasfound that air bubbles of carbon dioxide retained irregularly in aregion of a part of the flow path, and the shortage of fuel supplyoccurred irregularly in a region of a part of the electromotive portionunit.

In the direct type methanol fuel cell power generator 900, as describedabove, the reinforce member 934 was formed. Thus, it was verifiedpossible to decrease irregular fluctuation swing width of voltage outputas seen in FIG. 42 to an extent of 50% before troubleshooting.

Tenth Embodiment

FIG. 43 is a plan view and a sectional view showing a flow path plate1030 incorporated in a direct type methanol fuel cell power generator1000 (not shown) according to a tenth embodiment of the presentinvention. These plan view and sectional view are shown as required.

A mono-polar type flow path 1030 was formed by using an acrylic resinbeing an insulating resin. In the figure, reference numeral 1033designates a serial type flow path. A reinforce member 1034 is providedin the flow path 1033. The reinforce member 1034 has the thickness byabout 75% of the depth of the flow path.

EXAMPLE 10

A power generating operation test similar to that of Example 9 wascarried out in a mono-polar type flow path plate having formed thereonthe serial type flow path used in Example 8. Further, the abovemono-polar type flow path plate was compared with a flow path plate onwhich troubleshooting of a comb-shaped structure portion was carried outby forming the reinforce member 1030 as shown in FIG. 43. As a result,as in Example 9, it was verified that a voltage fluctuation appearingbefore troubleshooting decreased to about 40% before troubleshooting.

As has been above, in the direct type methanol fuel cell power generator100 according to the present embodiment, a deflection in output on anelectromotive portion unit by unit basis is reduced and a stable fuelsupply can be carried out. Thus, a stable output can be obtained.

Eleventh Embodiment

FIGS. 44A to 44C are views each showing a flow path plate incorporatedin a direct type methanol fuel cell power generator 1100 (not shown)according to an eleventh embodiment of the present invention. Thefigures show first to third flow path plates 1110, 1130, and 1150. Anacrylic resin being an insulating resin was used as a material for eachof the flow path plates. A mono-polar type flow path plate 1130comprising a parallel type flow path was used. In the figures, referencenumerals 1111, 1112, 1131, 1132, 1151, and 1152 each designate a goldribbon, and reference numerals 1113, 1133, and 1153 each designate aflow path. In addition, reference numeral 1134 designates a reinforcemember.

A parallel type flow path used in the direct type methanol fuel cellpower generator 600 cannot be formed in a shape penetrating the top andbottom of a flow path plate unlike the direct type methanol fuel cellpower generator 700 or direct type methanol fuel cell power generator800 because a comb-shaped structure portion is not supported from theperiphery of the flow path plate. In the direct type methanol fuel cellpower generator 1100, by providing the reinforce member 1134, it hasbeen possible to form a flow path in the shape penetrating the top andbottom of the flow path plate.

EXAMPLE 11A

FIG. 45 is a view showing a current voltage characteristic when theabove-described direct type methanol fuel cell power generator 1100 hasbeen operated under the operating condition of Example 9 (or Example10). As is seen from FIG. 45, as in Example 6, it was observed that anoutput was unstable due to a deflection in fuel supply amount withrespect to two electromotive portion units arranged on the same plane.However, as in Examples 7 and 8, it was verified that an outputdifference between the sets of the top and bottom electromotive portionunits decreases.

In addition, as in Examples 9 and 10, it was found possible to suppressa disposition of flow paths while in tightening or power generation orto prevent short-circuit or closing between the flow paths by means ofthe reinforce member formed in the flow path. Further, in the case offorming a stripe shaped flow path failing to comprise an externalmanifold, it was found very effective in preventing an island shapedportion in a flow path partitioning a flow path from completely slippingoff from the periphery of the flow path plate.

EXAMPLE 11B

FIG. 46 is a view showing a current voltage characteristic when theabove-described direct type methanol fuel cell power generator 1100 hasbeen operated under the operating condition of Example 9 or Example 10.In Example 9, when continuous operation was carried out at a temperatureof 70° C. and at a current density of 75 mA/cm² for one hour, a decreasein voltage output fluctuation of about 50% was achieved as shown in FIG.42. However, a slight fluctuation of voltage output was observed. Inthis regard, if continuous operation in the same condition was carriedout in a visualized state, it was found that air bubbles of carbondioxide produced in the flow path were carried and retained in thereinforce member, which caused regular fluctuation of voltage output.

Some of the materials for which the thickness of the reinforce member ofthe flow path plate used in Example 9 is reduced in a stepwise mannerwith respect to the depth of the flow path were formed, and an attemptwas made to investigate dependency on fluctuation of a voltage output.

It was clarified that a voltage fluctuation decreased rapidly by thethickness of the reinforce member being equal to or smaller than about50% to 40% with respect to the depth of the flow path. Also in a flowpath visualization operation, it was verified that the one-second ormore retention of carbon dioxide by the reinforce member did not occurin thickness equal to or smaller than the above thickness.

Moreover, the retention of air bubbles of carbon dioxide by thisreinforce member is more likely to occur as the sectional view of thereinforce member becomes closer to be vertical to the sectional view ofthe flow path. In order to decrease the retention of air bubbles ofcarbon dioxide more remarkably, it was found preferable to set to anacute angle the sectional view of the reinforce member against adirectional face on which a fuel or an oxidizing agent advanced.

As has been described above, in the direct type methanol fuel cell powergenerator 1100 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Twelfth Embodiment

FIG. 47 is a view showing a flow path plate 1230 incorporated in adirect type methanol fuel cell power generator 1200 (not shown)according to a twelfth embodiment of the present invention.

On the flow path plate 1230, gold ribbons 1231 and 1232 were clawed soas to come into intimate contact with a reinforce member 1234, andfurther, were brought into intimate contact with the member by using acyano acrylate based adhesive agent. During intimate contact, theadhesive agent was applied to only a portion of the reinforce membersuch that a site of the gold ribbons 1231 and 1232 coming into contactwith an electromotive portion unit is not covered with the adhesiveagent. Reference numeral 1233 designates a flow path.

EXAMPLE 12

In the above-described direct type methanol fuel cell power generator1100 using the mono-polar type flow path plate in Example 11B, it isverified that, if one-hour continuous operation is carried out under acurrent density of 75 mA/cm² at 70° C. for one hour, the gold ribbons1131 and 1132 are slackened in the center direction of the flow path,and the retention of air bubbles of carbon dioxide occurs due to suchslackness. In addition, it was verified that, after the above operationhad been repeated several times, the breakage of the gold ribbons 1131and 1132 occurs due to expansion or contraction of an electromotiveportion unit on rare occasion.

EXAMPLE 13

In the direct type methanol cell power generator 1200, even in the casewhere one-hour continuous operation had been repeated some tens of timesunder a charge current of 75 mA/cm2 at a temperature of 70° C. for onehour, no deformation or deflection of the gold ribbons occurred, andfluctuation or lowered output of a voltage output due to a failure of aconductive member was successfully prevented.

In the case where power collection from an electromotive portion iscarried out by a conductive member, the conductive member must be routedin the planar direction of the flow path plate. In view of a situationin which contact with an electromotive portion is obtained, there is aneed to use as a conductive member a precious metal or a base metalmember coated with the precious metal, or a carbon which is prone to becomparatively higher in resistance. However, as routing of theconductive member is longer, the cost becomes higher in the case wherethe member is made of a precious metal. In the case where the member ismade of a carbon material, an electrical resistance cannot be ignored.That is, there is a need to arrange conductive members in a distance asshort as possible, and as in this Example, a situation that the flowpath must be unavoidably crossed occurs. In such a case, it was verifiedpossible to avoid unnecessarily covering the surface of theelectromotive portion unit with the electromotive member as well as toprevent a malfunction such as short-circuit between the conductivemembers while in power generation.

As described above, in the direct type methanol fuel cell powergenerator 1200 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Thirteenth Embodiment

FIGS. 48A and 48B are a plan view and a sectional view showing a flowpath plate 1330 incorporated in a direct type methanol fuel cell powergenerator 1300 (not shown) according to a thirteenth embodiment of thepresent invention. These plan view and sectional view are shown asrequired. FIG. 49 shows a flow path plate before forming a penetratingportion. FIGS. 50A to 50C are sectional views each showing a process forforming the penetrating portion.

The flow path plate 1330 has an alternate type flow path 1333, and areinforce member 1334 is provide inside of the flow path. As shown inFIG. 48A, a site Q which is not covered with the anode electrode orcathode electrode is provided by several millimeters between theelectromotive portion units formed in the same electromotive portionunit layer. At this site Q, since no reaction occurs, there is no needto expose the flow path 1333 to the surface of the flow path plate 1330.Therefore, after a boundary wall 1335 has been left on the flow pathplate 1330, a tunnel shaped penetrating portion 1336 is formed on theboundary wall 1335. At this time, an outlet or an inlet of thepenetrating portion 1336 was formed so as to be set at a position of 1.0mm in the electrode inward direction of the anode electrode or cathodeelectrode from the end of the anode electrode or cathode electrode.

In a method for forming the penetrating portion 1336, as shown in FIGS.49 and 50A, the flow path 1333 is formed while leaving the boundary wall1335 being a boundary of the electromotive portion units. At the sametime, a supply port 1333 a and an ejection port 1333 b are formed. Then,as shown in FIG. 50B, a through hole is cut by drilling it from a sideface of the boundary wall 1335 to form the penetrating portion 1336.

EXAMPLE 13

According to the thus configured direct type methanol fuel cell powergenerator 1300, it is possible to prevent an occurrence of closing of aflow path, short-circuit between the flow paths, or leakage of the fueland oxidizing agent. That is, in an electromotive portion unit, anelectrolyte film swells during operation, and a sealing member may bedeflected. Thus, there can occur closing of a flow path positionedbetween the adjacent electromotive portion units in the sameelectromotive portion unit layer, or short-circuit of a fuel or anoxidizing agent on a line on which an end of the electromotive portionunit crosses a flow path. Therefore, it was found that the lowering ofan output occurred.

On the other hand, when a flow path plate was formed by aligning aninlet and an outlet of a tunnel-shaped structure with an end face of theanode electrode or cathode electrode, there occurred a phenomenon thatan oxidizing agent and a fuel short-circuit between the adjacent flowpaths after passing a gap produced at a contact portion between a crosssection of the electrode and a cross section of the silicon rubber resinsealing member.

Therefore, it is desirable that the inlet and outlet of thetunnel-shaped structure be positioned inside of the anode electrode andcathode electrode. However, as the position to be formed is deeper inthe inner direction of the anode electrode or cathode electrode, an areafacing the cathode electrode of the flow path is reduced, and powergeneration efficiency is considered to be impaired.

According to a test, when the inlet and outlet were formed at the insideby 0.5 mm, there occurred a phenomenon that, after an operation test fora long period of time, a fuel and an oxidizing agent short-circuit dueto contraction of an electrolyte film or silicon rubber resin sealingmember on rare occasion. Further, when the inlet and outlet were formedat the inside by 1 mm, no failure was observed.

From these facts, it was found desirable to position the inlet andoutlet of the penetrating portion by about 1.0 mm in the inwarddirection of the anode electrode and cathode electrode. Even in the caseof using an anode electrode or a cathode electrode of a small area suchthat a loss of fuel supply in an area having a width of 1 mm inperiphery cannot be ignored, it was found desirable to position theinlet and outlet at the inside of about 0.5 mm in order to preventshort-circuit or leakage.

With respect to the shape of an alternate type flow path, in order toachieve the feature more effectively, it is concluded preferable toreciprocate or encompass between a plurality of electromotive portionunits or electrodes arranged in parallel on the same plane. However, asa result, there is higher possibility that a flow path faces a sealingmember using a silicon based or Teflon based member. In particular, itwas found important to form the tunnel-shaped structure in the flow pathas shown in this Example in achieving the features of the shape of thealternate shape flow path.

In addition, it was found that such a tunnel-shaped structure waseffective to the flow path portion positioned between the supply port orthe ejection port of the flow path port and the electrode. Further, sucha tunnel-shaped structure is not realistic from the viewpoint ofrigidity in applying the structure to a brittle member such as a carbon.The above tunnel-shaped structure is significantly effective in the caseof using the above-described insulating resin member.

FIGS. 51A to 51E and 52A to 52F are plan views each showing a modifiedexample in which a boundary wall is provided on a flow path plate, and apenetrating portion is provided on the boundary wall. In these figures,reference numeral 1360 denotes a flow path; 1361 and 1362 denote asupply port and an ejection port; 1363 denotes a reinforce member; and1364 denote a boundary wall. A penetrating portion (not shown) isprovided at the inside, and a plurality of flow paths 1360 are connectedto each other. Reference numeral 1370 denotes a range in which the anodeelectrode or cathode electrode comes into contact with the flow pathplate.

As described above, in the direct type methanol fuel cell generator 1300according to the present invention, a deflection in output on anelectromotive portion unit by unit basis is reduced and stable fuelsupply can be carried out. Thus, a stable output can be obtained.

Fourteenth Embodiment

FIGS. 53A to 53C are views each showing a flow path plate incorporatedin a direct type methanol fuel cell power generator 1400 according to afourteenth embodiment of the present invention.

FIGS. 53A and 53B are views each showing a flow path plate 1400 having apenetrating portion. As the flow path plate 1400, there is shown anexample when the plate is formed by pasting two resin material basedplanar members 1410 and 1420. FIG. 53B is a complete view showing theflow path plate 1400 formed by bonding and pasting the two planarmembers 1410 and 1420. The planar member 1400 has a member main body1411, and at this member main body 1411, a site serving as each portionof the flow path plate 1400 is formed after assembled. Reference numeral1412 denotes a hole portion forming portion for forming an ejection portand a supply port; 1413 denotes a boundary wall forming portion; 1414denotes a reinforce member forming portion; 1415 denotes a flow pathforming portion; and 1416 denotes a comb-shaped structure portionforming portion.

Similar, the planar member 1420 has a member main body 1421, and at thismember main body 1411, a site serving as each portion of the flow pathplate 1400 is formed after assembled. Reference numeral 1422 denotes ahole portion forming portion for forming an election port and a supplyport; 1423 denotes a reinforce member forming portion; 1425 denotes aflow path forming portion; and 1426 denotes a comb-shaped structureportion forming portion.

The flow path forming portions 1415 and 1425 of the planar members 1410and 1420 are formed to produce a mirror image when both of them arepasted with each other. The thickness of a portion of the boundary wallforming portion 1413 is formed to be smaller than the thickness of themember main body 1411 so as to produce the same plane as the surface ofthe planar members 1410 and 1420 in a face opposite to a face on whichthe planer members 1410 and 1420 are pasted with each other. It isdesirable that the width of the flow path forming portion 1415 is formedto be equal to the width of the flow path forming portion 1425; thethickness of this forming portion is equal to or smaller than a half ofthe thickness of the member main body 1411 and is equal to or greaterthan the thickness such that the strength is sufficient.

The boundary wall forming portion 1413 may be formed at both of theplanar members 1410 and 1420. Thus forming portion may be formed to beequal to a total of the thicknesses of these members and at only eitherof reference numerals 4601 a and 4602 b. However, it is desirable that atotal of the thicknesses of the reinforce member forming portions 1414and 1424 is equal to or smaller than a total of the thicknesses of themember main bodies 1411 and 1421 and is equal to or greater than 0.2 mm.In addition, it is desirable that this forming portion is formed so asto have the same surface on the face sides to be pasted with each other.In the case where the reinforce member forming portions 1414 and 1424are formed at both of the planar members 1410 and 1420, it is desirablethat the above forming portion is formed so as to produce the same planeas the surface of the planar members 1410 and 1420 in the faces of theplanar members 1410 and 1420 to be pasted with each other.

In adhering and pasting these planar members 1410 and 1420, it ispreferable to use an adhesive agent made of cyano acrylate or the likeand a polymer alloy type thermosetting resin in consideration ofchemical resistance, heat resistance, and water resistance. Athermosetting type epoxy resin based adhesive agent or the like may beselected according to adaptability or operating state between thematerial and adhesive agent of the planar members 1410 and 1420. Inorder to prevent closing of a flow path, it is desirable that anadhesive agent be applied as uniformly and thinly as possible on theoutermost surface at the side of the adhesive face of the planar members1410 and 1420.

In the flow path plate having the penetrating portion, it was verifiedthat closing of the flow path, short-circuit between the flow paths, orleakage of a fuel and an oxidizing agent was eliminated. On the otherhand, the sectional view of a through hole is shaped in a circle whosediameter is smaller than the depth of the flow path. Thus, it wasobserved that there occurred a significant fluctuation in voltage outputdue to retention of air bubbles of carbon dioxide as observed inExamples 12 and 13. With respect to the retention of air bubbles ofcarbon dioxide, the lowering of output with the air bubbles of carbondioxide was observed for 30 minutes or more during a maximum of one-houroperation. This lowering is considered to have been produced as a resultof clogged air bubbles because a sectional area of the penetratingportion on the flow path plate of Example 13 is small.

Therefore, there is a need to increase the sectional area of thepenetrating portion. However, such increase of the sectional area istechnically difficult in a method for drilling a through hole by using adrilling machine after forming a flow path plate, as shown in Example13. Even if injection molding is used, the desired cross sectionalmember is installed before molding, and is removed after the molding.Thus, it is considered that as the number of electromotive portion unitsincreases and as the flow path return count increases, the processes orsteps of forming the penetrating portion become very complicated.

In the flow path plate 1400 according to the present embodiment, theflow path plate having a rigid tunnel structure can be easily formed byadhering only at least one set of two members having no penetratingportion formed by injection molding. In addition, in adhering members toeach other, it is preferable to use an adhesive agent with a cyanoacrylate based and polymer alloy type thermosetting resin inconsideration of chemical resistance, heat resistance, and waterresistance.

EXAMPLE 14

In a mono-polar type flow path plate 1400 on which acryl is used as aflow path member to be formed above, and a conductive member 1430 isformed as shown in FIG. 53C, a desired penetrating portion can be easilyformed. In a one-hour continuous power generating operation under whichvisualization of a flow path using this flow path plate 1400 was carriedout, the retention of air bubbles was equal to or smaller than 10seconds at most, and a good power generation state was obtained.

As has been described above, in the flow path plate 1400 incorporated inthe direct type methanol fuel cell power generator according to thepresent embodiment, a deflection in output on an electromotive portionunit by unit basis is reduced and stable fuel supply can be carried out.Thus, a stable output can be obtained.

Fifteenth Embodiment

FIGS. 54A and 54B is a view showing a flow path plate 1500 having formedthereon a penetrating portion, the flow path plate being incorporated ina direct type methanol fuel cell power generator according to afifteenth embodiment. The flow path plate 1500 is shown as an examplewhen the plate is formed by pasting three resin material based planarmembers 1510, 1520, and 1530. FIG. 54B is a complete view showing theflow path plate formed by adhering and pasting the planar members 1510to 1530 of FIG. 54A.

When the flow path plate is further reduced in thickness, it may bedifficult to form a tunnel-shaped structure. However, unlike a case of aflow path plate requiring conductivity, it is possible to provide aninsulating resin based thin film which does not require corrosion orconsideration of a technique for forming an extremely thin plate to bebrought into intimate contact with a full face of the flow path plate.

FIGS. 54A and 54B each show an example when a flow path plate formed ina tunnel-shaped structure is formed by pasting the three planar members1510 to 1530. FIG. 54B is a complete view showing a flow path plateformed by adhering and pasting the three members of FIG. 54A.

The planar member 1520 serves as a base portion of a flow path when theflow path plate of FIG. 54B is formed. Each of the planar members 1510and 1530 primarily serves as a cap for forming a penetrating potion. Inthe figures, reference numerals 1511, 1521, and 1531 each denote asupply port forming portion or an ejection port forming portion; 1512,1522, and 1532 each denote a flow path forming portion; 1523 denotes areinforce member of a flow path; 1514, 1524, and 1534 each denote apenetrating port forming portion; 1515, 1525, and 1535 each denote acomb-shaped structure forming portion; and 1536 denotes a boundary wallon which a penetrating portion is formed.

It is desirable that the thickness of the planar members 1510 and 1530is equal to or smaller than a half of the thickness of the planar member1520 and is equal to or greater than the thickness such that thestrength thereof is sufficient. It is desirable that the thickness ofthe reinforce member 1523 is equal to or smaller than a half of thethickness of the completed flow path plate and is equal to or greaterthan 0.2 mm.

A method for adhering and pasting these planar members 1510 to 1530 isidentical to that in the case of Example 14. An adhesive agent may beapplied to both faces of the planar member 1520 or an adhesive agent maybe applied to the adhesive face side of the planar members 1510 and1530.

In accordance with the above-described process, in a flow path plateformed by using an acryl resin of 1.5 mm in thickness for a memberserving as a base station of the flow path plate and by using apolyimide resin film of about 0.2 mm in thickness for a capping portion,the following results were obtained.

EXAMPLE 15A

During one-hour continuous power generating operation, no retention ofair bubbles of carbon dioxide of several seconds or more was observed,and a good power generation state was successfully maintained.

EXAMPLE 15B

By using the flow path plate used in Example 15A formed of an acrylicresin, when continuous operation under a charge current of 70 mA/cm² at70° C., it was observed that an output was gradually lowered aroundabout three hours, as shown in FIG. 55, and the output was hardlyobtained after six hours. When a stack was dissembled after thecompletion of operation, it was found that a methanol aqueous solutionfuel and an air were not normally supplied due to deformation of amember with a temperature increase.

Then, a poly-carbonate resin having a heat deformation temperature of140° C. to 150° C. was used, a flow path plate shaped in the same way asin Example 15 was formed, and continuous operation under a chargecurrent of 75 mA/cm² at 70° C. was carried out. As shown in FIG. 55,after continuous operation of about 200 hours, it was observed that anoutput is lowered by about 10%. After dissembling the stack, when astate of the flow path plate was checked, it was verified that fineirregularities were produced on a surface of the flow path plate by thepresence of carbon paper provided in the electromotive portion unit.Further, it was verified that slight distortion occurred with the entireflow path plate.

Furthermore, in a polyether imide resin or polyimide resin having ahigher heat deformation temperature, as shown in FIG. 55, it wasobserved that an output is lowered by about 5% in continuous operationof 300 hours or more as well. After dissembling the stack, no damage orchange was observed on the surface of the flow path plate. In addition,from a result obtained by using a normal carbon based flow path plate,it was clarified that the output lowering of about 5% is due to theoutput lowering of the electromotive portion unit itself.

From the above result, it was clarified that a fuel cell flow path platecapable of making safe operation over a long period of time can beformed only in a resin member having at least a heat deformationtemperature which is higher than an operation temperature by 100° C. ormore.

The resin member used for the flow path plate described above must besufficiently endurable to a temperature at which power is generated. Onereason is that it is desired that heat deformation over a long period oftime can be ignored with respect to a stack or fuel temperature duringpower generation. What is more important is that, while in actual powergenerating operation, a temperature of the cathode electrode surface inthe electromotive portion unit is further higher than the stack or fueltemperature. A rise of 100° C. higher than the stack internal surfacetemperature is occasionally indicated depending on an operatingcondition for the fuel cell power generator. This indicates that a resinmember having a heat deformation temperature at a point higher than atleast 100° C. must be used as a flow path plate.

Therefore, in the case where an environment temperature of the fuel andstack is assumed to be 40° C. to 50° C., first, polyether imide resin,polyimide resin, polyamide imide resin, polysulfone resin, polyethersulfone resin, melamine phenol resin, or silicon resin, reliably havinga heat deformation temperature at a temperature of 140° C. or more isused as a desired resin member for flow path plate. Next, in anoperating condition for a fuel cell which is further close to a roomtemperature, it is preferable to apply polycarbonate resin, heatresistance vinyl ester resin, bis-phenol F-type epoxy resin, polyamideresin, polybutylene telephthalate resin or the like. In addition, at atemperature other than the above as well, it is concluded preferable touse a resin member whose temperature is higher than the stack surfacetemperature by 100° C. or more as a flow path plate.

As has been described above, in the direct type methanol fuel cell powergenerator 1500 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit basis is reduced andstable fuel supply can be carried out. Thus, a stable output can beobtained.

Sixteenth Embodiment

FIGS. 56A and 56B are views each showing a direct type methanol fuelcell power generator 1600 according to a sixteenth embodiment of thepresent invention. FIG. 56A is a longitudinal cross section showing thepower generator. FIG. 56B is a transverse cross section showing thepower generator. FIGS. 57A to 57E are sectional views taken along δ1-δ1to δ5-δ5 in FIGS. 56A and 56B.

The direct type methanol fuel cell power generator 1600 was formed by apolyether imide resin for which long stability of the flow path plateused in Example 15 was demonstrated as described later such that theflow path plates 1622 to 1624 are integrated with a pipe and a fueltank, as shown in FIG. 49.

The direct type methanol fuel cell power generator 1600 comprises acabinet 1610, a stack portion 1620 held by this cabinet 1610, a supplyportion 1630 for supplying a fuel and an oxidizing agent to this stackportion 1620, and a fuel and oxidizing tank portion 1650 removablyprovided at the cabinet 1610.

At the stack portion 1620, a set of electromotive part units having twoelectromotive units arranged in a horizontal direction is arranged onthe top and bottom of one mono-polar type flow path plate 1623. Amethanol aqueous solution fuel is supplied to the flow path plate 1623.In addition, on the mono-polar type flow path plate 1623 and the flowpath plates 1624, 1624 disposed at the top and bottom of fourelectromotive portion units, flow paths 1622 a and 1624 a are formedonly on a face on which the electromotive portion units are arranged, sothat air is supplied.

A tightening plate 1621 comprising a heat insulating material isinstalled on the outermost surface of the stack portion, and sealing iscarried out by a sealing member included in the stack by using atightening tool (not shown).

In the thus configured direct type methanol fuel cell power generator1600, operation is carried out as follows. That is, air is fed to thestack portion 1610 by means of an air supply pump 1631, and the fed airflows through a supply channel 1632 for air supply formed at theoutermost portion of the mono-polar type fuel flow path plate. At aportion 1633 penetrating in a stacking direction, the air is branchedinto flow paths of the top and bottom flow path plates 1622 and 1624.The air and steam having passed through a part of an electromotiveportion unit meet the outermost ejection portion 1635 of the mono-polartype flow path plate at another penetrating port 1634. Then, the air andsteam inflow a space 1636 for temporarily holding a methanol aqueoussolution fuel.

On the other hand, the methanol aqueous solution fuel is fed from thespace 1636 by means of a liquid supply pump 1641. The fed fuel flowsthrough a fuel liquid supply channel 1637. After the fuel has flowedthrough the stack, the fuel inflows the space 1636 again together withcarbon dioxide. A supply channel 1737 for supplying methanol with highconcentration from a methanol cartridge 1651 by means of a highconcentration methanol supply pump 1638 is formed in the space 1636.

EXAMPLE 16

In operation, the initial concentration of a methanol aqueous solutionfuel was defined as 3 mol/l; a fuel flow rate was defined as 0.04cm/min; and an air flow rate was defined as 40 cm/min. As a result ofthe operation, a temperature of the stack portion increased only toaround 50° C. However, the leakage of the supplied air and methanolaqueous solution fuel was not observed. In addition, while distortion orthe like was not observed with a flow path plate 4902 or the lineincluding a space 4907 or the like, it was verified that continuousoperation of 300 hours can be carried out.

In general, in a fuel cell power generator, a fuel container, a pipe,and a stack are handled as independent constituent elements, and thewhole configuration is provided by combining these elements with eachother. However, in a fuel cell power generator applied to use of aportable electronic device, there occurs a need to reduce equipment inthickness as well as structural simplification. Therefore, with respectto a stack included, it is preferable to arrange electromotive portionsin parallel such that the number of stacks is remarkably reduced andsuch that a planar direction of electromotive portion units is parallelto a direction which is vertical to the thickness of equipment. Thisdenotes that there occurs a need to reduce a pipe in thickness in orderto supply or eject a fuel or an oxidizing agent with respect to a stackand that it becomes extremely difficult to apply piping to a side faceof the flow path plate because the flow path plate is reduced inthickness. Further, it becomes difficult to maintain rigidity ofequipment because the above plate is reduced in thickness. It ispreferable that a fuel container or pipe be made of a resin, and thecontainer or pipe made of the resin will suffice. However, in asituation in which the entire equipment must be specialized to ensurereduction in thickness, when the constituent elements are formeddependently, consideration must be taken into a structure for connectinga supply port or an ejection port of a stack fuel or oxidizing agent toa fuel container or pipe, or a structure for increasing the wholerigidity.

On the other hand, in the direct type methanol fuel cell power generator1600, it becomes possible to produce a portion of a pipe or fuelcontainer as an extension of a flow path plate, i.e., to form a tank ora pipe to be integrally molded by means of a resin member which isidentical to the flow path plate. Thus, remarkable reduction in numberof constituent parts and structure rigidity of a fuel cell powergenerator due to integration are easily achieved at the same time,making it possible to significantly improve productivity. In the casewhere a flow path plate is formed of a material consisting essentiallyof a carbon or is formed of a metal, it is very difficult to ensure suchsignificant improvement. Thus, a material for the flow path plates 1622to 1624 is required to be a resin material.

As has been described above, in the direct type methanol fuel cell powergenerator 1600 according to the present embodiment, a deflection inoutput on an electromotive portion unit by unit is reduced and stablefuel supply can be carried out. Thus, a stable output can be obtained.

In the above-described direct type methanol fuel cell power generator1600, there may be provided an electric circuit 1660 for supplying apart of the power output obtained from the electromotive portion unitgroup to the liquid supply pump 1641; and the high concentrationmethanol supply pump 1638 and the air supply pump 1631 and for supplyingthe remaining power output to the external electric device.

In FIG. 56A, reference numeral 1661 denotes a gas-liquid separatingmechanism for separating only a gas component from a dischargedsubstance of the anode electrode; reference numeral 1660 denotes theelectric circuit for supplying a part of the power output obtained fromthe electromotive portion unit group to the liquid supply pump 1641 andthe high concentration methanol supply pump 1638 and for supplying atleast a part of the remaining power output to the external electriccircuit.

In this manner, even in the case where a part of the power output hasbeen supplied to the external electric device, it has been successfullyverified that good power generating operation can be carried out in thesame manner as in Example 16.

In FIG. 58, in the direct type methanol fuel cell power generator 1600,a charge current output on a four-electromotive portion unit basis wasset to 0.75A, and a methanol water solution fuel concentration and afuel flow rate were changed, whereby a power generation test was carriedout. An air supply amount was set to 240 ml/min.

As is evident from Formula III or mathematical formulas 3 and 4, inpower generation, 6 electrons can be obtained from one molecule ofpaired methanol and water. Thus, in order to obtain a current of 1A by asingle electromotive portion unit, methanol and water of 1.725 (mol/s)are obtained as a supply amount which is a theoretically minimumrequirement. In addition, in the case where there are provided “n”electromotive portion units which are electrically wired in series or inparallel, a supply amount of 1.725×n (mol/sec) is required as atheoretical amount.

This denotes that: a theoretical supply amount of 34.5 (ml/min) isrequired to obtain a current of 1 A from a single electromotive portionunit in the case where a fuel having concentration of 3 mol/l is used; atheoretical amount of 51.8 (ml/min) is required in the case where a fuelhaving concentration of 2 mol/l is used; and a theoretical amount of 104(ml/min) is required in the case where a fuel having concentration 1mol/l is used; and a theoretical supply amount of 25.9 (ml/min) isrequired in the case where a fuel having concentration of 4 mol/l isused.

Further, in the case where a current of 1A is obtained from each of “n”electromotive portion units, a supply amount which is “n” times as muchas these supply quantities is required as a total amount.

From FIG. 58, in fuel concentration of 3 mol/l, it is found that amaximum voltage is obtained in a supply amount of methanol watersolution fuel of about 0.17 ml/min, and similarly, no maximum value isobtained in a supply amount of about 0.3 ml/min in fuel concentration of2 mol/l and in 0.8 ml/min in fuel concentration of 1 mol/l. On the otherhand, it is found that, in fuel concentration of 4 ml/min, although amaximum value is obtained in about 0.12 ml/min, the maximum value isslightly lower than a value in 3 mol/l, and a decrease of the maximumvalue is significant in 5 mol/l. Table 1 summarizes these results.

TABLE 1 Voltage value (V) in Theoretical Concen- charge current of 0.75A supply amount tration Supply amount (μ/min) in charge (mol/l) 176(μl/min) 400 (μl/min) 800 (μl/min) current of 0.75 A 1 0.00 1.28 1.44312 2 1.28 1.36 1.36 156 3 1.20 1.12 1.04 104 4 1.08 0.80 0.00  78

As is evident from Table 1, it is found that the maximum voltageobtained at each concentration cannot be reached or no voltage can beobtained; and that a value equal to or greater than 90% of the maximumvoltage can be obtained in a supply amount which is about 1.5 to 2.0times the theoretical amount. However, in the case of a supply amountmore than the above range, a one-sided voltage drop is observed.

Moreover, in a concentration of about 4 mol/l or more, lowering of themaximum voltage value with a rise of concentration is significant. It ispreferable to use a maximum of methanol water solution fuelconcentration of about 5 mol or less. In the case of low concentration,a supply amount which is much more than 2 times the theoretical amountis required. Thus, it is found preferable to use methanol water solutionfuel concentration of at least 1 mol/l or more in order to reduce apressure loss subjected from the flow path plate, and to save powerconsumption of a complementary device.

That is, it is found that a condition for methanol water solution fuelconcentration and supply amount is proper, the condition meetingFormulas (101) to (103).

In the above-described embodiments and Examples, although only a fuelflow path is of alternate type, an air flow path may be of alternativetype. In addition, both of the fuel flow path and the air flow path maybe of alternate type.

The present-invention is not limited to the above-described embodimentsas is. At the stage of implementation, constituent elements can beembodied by modifying them without deviating from the spirit of theinvention. In addition, a variety of inventions can be formed by using aproper combination of a plurality of constituent elements disclosed inthe above-described embodiments. For example, some constituent elementsmay be deleted from all the constituent elements disclosed in theembodiments. Further, the constituent elements over the differentembodiments may be combined with each other as required.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A direct type liquid fuel cell power generator, comprising: anelectromotive portion unit group composed of a plurality ofelectromotive portion units formed by sandwiching an electrolyte filmbetween an anode electrode including an anode catalyst layer and acathode electrode including a cathode catalyst layer; a first flow pathplate having formed thereon a first flow path which is disposed inabutment with the anode electrode of the electrode portion unit groupand through which a fuel flows; and a second flow path plate havingformed thereon a second flow path which is disposed in abutment with thecathode electrode of the electrode portion unit group and through whichan oxidizing agent flows; wherein the electromotive portion units areinterposed between the first flow path plate and the second flow pathplate and have different electrolyte films, and wherein the first flowpath passes so as to come into contact with all anode electrodes of theelectromotive portion unit group without branching from an inlet thereofto an outlet, and is formed so as to come into contact with an anodeelectrode of at least one electromotive portion unit a plurality oftimes.
 2. A direct type liquid fuel cell power generator according toclaim 1 comprising: meeting the following condition:Y≦Y ₀×2  (101)Y ₀=1.04×10⁻⁴ ×nI/C _(MeOH)  (102)1.0≦C_(MeOH)≦5.0  (103) wherein “n” denotes the number of electromotiveportion units which the electromotive portion unit group has; I denotesa current outputted by each electromotive portion unit; C_(MeOH) denotesa concentration of a methanol aqueous solution fuel to be supplied; Ydenotes a total amount (l/min) of the methanol aqueous solution fuelsupplied to the electromotive portion unit group; and a temperature ofthe each electromotive portion unit is within the range from 40° C. to70° C.
 3. A direct type liquid fuel cell power generator according toclaim 1, comprising: a liquid fuel supply device which supplies a liquidfuel to the flow path plate which comes into contact with an anodeelectrode of the electromotive portion unit group; an oxidizing agentsupply device which supplies an oxidizing agent to the flow path platewhich comes into contact with a cathode electrode of the electromotiveportion unit group; a liquid fuel container which houses a liquid fueland supplies the liquid fuel to the liquid fuel supply device; agas-liquid separating mechanism which separates only a gas componentfrom a discharged matter of the anode electrode; and an electric circuitwhich supplies a part of a voltage output obtained from theelectromotive portion unit group to the liquid fuel supply device andthe oxidizing agent supply device and supplies at least a part of theremaining power output to external electric equipment.